where to get tax advice

[rasselbiluga]

Besides investing in Japan with Rakuten, I am also investing in Ireland-domiciled, accumulating ETFs with IKBR. I am not sure if I will stay in Japan long-term, so the advantage of the ETFs is that I could keep them in case I would leave Japan, whereas I would need to close my Rakuten account.
I am trying to find out how the Japanese tax office treats these ETFs and whether I will need to file a tax return. These ETFs are accumulating, so dividends are re-invested internally. In the case of Japanese mutual funds, if dividends are re-invested internally, no taxes are due. The question is whether this is also true for accumulating ETFs hold overseas. This question has already been discussed in some threads on this forum, but without definitive answer:
viewtopic.php?f=11&t=1331
viewtopic.php?f=8&t=817
viewtopic.php?f=11&t=1096
I know that in Europe, it depends on the country. Some countries such as Switzerland don't care whether the ETF is accumulating or distributing - you have to pay taxes in any case. Other countries don't tax internally re-invested dividends.
I am still a beginner and don't really know how to approach this. I did quite some online search (also searched the Japanese web using google translate), but couldn't find anything useful. How would the people of the forum tackle this? Is this something I could simply ask the Japanese tax office? Or is it possible to seek advice from a professional tax advisor just for this specific question? In the latter case, do the people here have any recommendations for a tax advisor in the Tokyo area?

[rhe]

I don't have specific experience with the NTA, but my impression from other countries is that if you submit a personal tax return in good faith, and they later decide that they disagree and that you owe them money, the penalties are likely going to small or potentially zero (other than the money that you owe them).

This question is sufficiently exotic that you would likely need a very highly qualified professional to answer it correctly, and my guess is the resulting fees would more than counterbalance any tax advantage. I think there are really only two reasonable things to do here:
1. Don't declare any dividends of these ETFs and wait for an audit
2. Choose distributing ETFs to avoid a pissed off tax auditor

My own portfolio is a mix of these two!

[rasselbiluga]

Thanks for your reply!

I don't have specific experience with the NTA, but my impression from other countries is that if you submit a personal tax return in good faith, and they later decide that they disagree and that you owe them money, the penalties are likely going to small or potentially zero (other than the money that you owe them).

Maybe you are right and I am thinking too much about it. I already imagine myself in a Japanese prison for tax evasion Well not really, but I am quite fearful about these things. Maybe I want to apply for permanent residency one day. What if it gets rejected because I did something wrong with my taxes... Bottom line is, I doubt I can have peace of mind without being sure I am doing things correctly.

This question is sufficiently exotic that you would likely need a very highly qualified professional to answer it correctly, and my guess is the resulting fees would more than counterbalance any tax advantage.

Indeed, probably a rather exotic question. Maybe I'm just going to ask an accountant whether they are willing to find out and how much that would cost. They can always say no. There were some suggestions for tax accountants in this thread.

I think there are really only two reasonable things to do here:
1. Don't declare any dividends of these ETFs and wait for an audit
2. Choose distributing ETFs to avoid a pissed off tax auditor

My own portfolio is a mix of these two!

Distributing ETFs is an interesting option I haven't thought about yet! At least there would be no doubt about how to declare it.

[Tkydon]

There are several qualifying questions with any Tax related enquiry:

1. Are you a US Citizen. If so, you are subject to Global Taxation in the US. (and you'll probably find it very difficult to invest anywhere else, as financial institutions don't want to deal with the tax implications)

2. Have you been living in Japan for more than 5 years? Are you treated as a Permanent Resident For Tax Purposes?
Whether you have actual Permanent Resident Status or not, if you have lived in Japan for more than 5 years in the last 10 years, then you are treated as a Permanent Resident for Tax Purposes, same as a Japanese. In this case you are subject to Global Taxation, on all global assets.
For this reason, many foreign business men choose not to stay in Japan more than 5 years.
There are rumours that this may be under review, to entice more foreigners to come to Japan, but as far as I know it is not yet finalised.

3. Does your country have a Tax Treaty with Japan?

https://www.mof.go.jp/english/policy/ta ... st_en.html

4. If the assets are in a country other than your country, does Japan have a Tax Treaty with that country?

The answer to your original question will change, depending on your answers to the four questions above.

I will assume; 1 Yes, 2 Yes, 3 Yes, 4 Yes

Dividends payable on US instruments are taxable in the US, whether you are a US Citizen or not, and Tax will be withheld by the financial institution, either at the standard rate of 30% or some lesser rate agreed in the Tax Treaty between the US and Japan.
I don't believe US Citizens can avail themselves of the Tax Treaty between the US and Japan.
However, everyone can claim a Credit for Foreign Taxes Paid on their Japanese Tax Return - See Page 47 of the 2020 Guide here:
https://www.nta.go.jp/english/taxes/ind ... /index.htm

Next Question.

5. Are the ETF Dividends taxed in the US prior to being reinvested? And do you receive a Statement of Taxes Withheld; either I-90 for US Citizens or I-94 for Foreign Nationals?

See Page 56 of above doc.

If you are a US Citizen, or a Foreign National who has not correctly filed a W8-BEN claiming the reduced Withholding Tax rate of 10% under the Tax Treaty between Japan and the US, Tax is withheld in the US at 30%, you've paid more than the tax would be in Japan. (15% National Tax on Dividend Income, 0.315% for Reconstruction Tax, and 5% Resident's Tax on Dividend Income.)
You could actually offset that Tax Credit against other Capital Gains if you chose to report it. If it's not such a large amount of money... It's probably not worth worrying about...

If you are a Foreign National (non-US Citizen) who has correctly filed a W8-BEN claiming the reduced Withholding Tax rate of 10% under the Tax Treaty between Japan and the US, Tax is withheld in the US at 10%. After claiming the Foreign Tax Credit, you would be subject to the remaining 5% National Tax on Dividend Income, 0.315% for Reconstruction Tax, and 5% Resident's Tax on Dividend Income. It's probably not worth worrying about...

They'll get you on the Capital Gains when you sell the ETFs...

Any Foreign National (non-US Citizen), including Japanese, who is filing a W8-BEN should in Part II state:

Part II Claim of Tax Treaty Benefits (for chapter 3 purposes only) (see instructions)
9. I certify that the beneficial owner is a resident of ___JAPAN___ within the meaning of the income tax treaty between the United States and that country.
10. Special rates and conditions (if applicable—see instructions): The beneficial owner is claiming the provisions of Article and paragraph
_10 2(b), 11 2(b)_ of the treaty identified on line 9 above to claim a ___10___ % rate of withholding on (specify type of income):
___Dividend and Interest Income___
Explain the additional conditions in the Article and paragraph the beneficial owner meets to be eligible for the rate of withholding:
___As A Resident Of Japan for Tax Purposes.___


If you choose to declare the Dividends, then you will have to follow this procedure>

March - File Japanese Tax Return
Declare the Gross Amount of the Overseas Income - i.e. Dividends Received - They will assess this amount @ 15%, 0.315% and 5%.
April - You will receive the I-90 or I-94 from the US Broker
If you are a US Citizen - File your US Tax Return
April/May - Refile your Japanese Tax Return - Fill the numbers from your I-90 or I-94 into the Foreign Tax Credit section of the Japanese Tax return.
You can do this anytime upto 3 years later... i.e. you could go back and claim Foreign Tax Credits for the last 3 years... They will then give you a refund.

[rhe]

Distributing ETFs is an interesting option I haven't thought about yet! At least there would be no doubt about how to declare it.

Actually....

You can find an ongoing argument online about the tax rate for dividends on (foreign) stocks held in a foreign brokerage account. Many accounting firms, including some of the most famous, hold that these dividends must be included in your income rather than taxed at the 20% rate. Other firms claim that this is wrong, and you can submit a tax return using 分離課税 and the 20% rate.

I asked at the local tax office, and was told -- by someone who seemed almost as confused as me -- that I had to include the dividends in income. I then spent a few hours messing around with the online NTA forms, and discovered that there was also a way to submit under the 20% rate. Who knows what an auditor will say.

The deeper point here is that asking an accountant will actually not get you certainty, because you can tell by looking at websites that you can get an accountant that will take your money and tell you that 20% is fine, but there is another equally well qualified accountant that will take your money and tell you that you can't use the 20% tax. To get even more extreme, even if the NTA forms were changed to prevent filing with foreign dividends under the 20% rate, that *still* doesn't mean that you can't use the 20% rate (in another country, I had a dispute with the tax authorities where their forms disagreed with the underlying tax law, and they eventually agreed with me that their forms were wrong). A court case might provide a final answer, but it looks like there either hasn't been one yet, or it isn't easily indexed on the internet.

[rasselbiluga]

Thanks Tkydon and rhe for your reply!

1. Are you a US Citizen. If so, you are subject to Global Taxation in the US. (and you'll probably find it very difficult to invest anywhere else, as financial institutions don't want to deal with the tax implications)

2. Have you been living in Japan for more than 5 years? Are you treated as a Permanent Resident For Tax Purposes?

Sorry I wasn't very precise in my original post.

1. I am not a US citizien
2. I am not yet a Permanent Resident For Tax Purposes, but will be next year.

3. Does your country have a Tax Treaty with Japan?

4. If the assets are in a country other than your country, does Japan have a Tax Treaty with that country?

The answer to your original question will change, depending on your answers to the four questions above.

I will assume; 1 Yes, 2 Yes, 3 Yes, 4 Yes

Dividends payable on US instruments are taxable in the US, whether you are a US Citizen or not, and Tax will be withheld by the financial institution, either at the standard rate of 30% or some lesser rate agreed in the Tax Treaty between the US and Japan.
I don't believe US Citizens can avail themselves of the Tax Treaty between the US and Japan.
However, everyone can claim a Credit for Foreign Taxes Paid on their Japanese Tax Return - See Page 47 of the 2020 Guide here:
https://www.nta.go.jp/english/taxes/ind ... /index.htm

Next Question.

5. Are the ETF Dividends taxed in the US prior to being reinvested? And do you receive a Statement of Taxes Withheld; either I-90 for US Citizens or I-94 for Foreign Nationals?

I am investing in Ireland-domiciled ETFs, so I think claiming a tax credit based on the Japan/US tax treaty does not apply here, right? The reason I chose Ireland ETFs is that Ireland does not withhold any tax on Ireland-domiciled ETFs, and Ireland has a tax treaty with the US at 15%. That's why, in general, it is advantageous for non-US investors to use Ireland-domiciled ETFs, as explained nicely in the bogleheads wiki. Japan is one of the rare cases where this is not true, at least for US stocks (see this table), because the Japan/US treaty is at only 10%. However, I am investing in globally diversified ETFs where the US has only a weight of ~60%, so the Ireland ETFs might still be better (because the US will withhold taxes on distributions from the 40% non-US securities hold by the ETF, while Ireland will not). In any case, even for non-US investors in Japan, Ireland-domiciled ETFs are a reasonable choice.

The deeper point here is that asking an accountant will actually not get you certainty, because you can tell by looking at websites that you can get an accountant that will take your money and tell you that 20% is fine, but there is another equally well qualified accountant that will take your money and tell you that you can't use the 20% tax

Well this isn't encouraging... I didn't expect it's that complicated.

Most of my savings (roughly 100k USD) are on a US bank account (because I lived there for some time). My plan was to gradually invest this over the next 1.5 years or so into accumulating, Ireland-domiciled ETFs using IKBR. The ideas behind the plan were:

1. I thought accumulating ETFs will not be taxable in Japan (since they don't distribute); hence, I would not even need to file a tax return (as long as I don't sell of course). However, as explained in the original post, not sure if this is really the case.
2. If I leave Japan, I don't need to sell the investments hold with IKBR (in contrast to the investments hold with a Japanese broker)

But if it is that complicated and unsure whether taxes are due for accumulating ETFs, and equally complicated to find out how the declare distributions from distributing ETFs, I might consider transferring my savings to Japan and invest here. It's just that transferring the money is not free, and if it turns out that I leave Japan after a few years, everything needs to be sold and transferred again...

[rhe]

Well this isn't encouraging... I didn't expect it's that complicated.

It's complicated in the sense that the law is uncertain, but I don't think that necessarily means that your response needs to be complicated. Tax authorities are underfunded, and their objective is to get people to pay the tax that they owe. If they think you owe more tax, they will tell you, with the objective of getting you to pay them that money. Their objective is to collect tax, not to run sting operations against people who paid at the 20% rate when they should have paid at the 43% rate. In other countries, whenever I had a disagreement with the tax authorities about the amount that I owed the only penalty I ever ended up paying was a small amount of interest because of delayed payment. As long as you're not actually doing something sneaky I don't think the uncertainty in the tax law presents much of a problem: just file a return taking a reasonable position, and if they disagree then you have to go back and pay a bit more.

Most of my savings (roughly 100k USD) are on a US bank account (because I lived there for some time).

If you buy an ETF that pays 2% dividends, then this is $2k dividends per year, which even at the highest possible tax rate would only be $1k per year of tax payable. I don't know the rule in Japan, but in the US I think they only go back 7 years max when they audit, so a reasonable worst case scenario would be that the NTA shows up a decade from now and tells you that you owe them ~$7k. Given your savings, this seems like an amount that wouldn't be too much trouble to pay!

[Tkydon]

Sorry I wasn't very precise in my original post.

I am not a US citizien
I am not yet a Permanent Resident For Tax Purposes, but will be next year.

I am investing in Ireland-domiciled ETFs, so I think claiming a tax credit based on the Japan/US tax treaty does not apply here, right? The reason I chose Ireland ETFs is that Ireland does not withhold any tax on Ireland-domiciled ETFs, and Ireland has a tax treaty with the US at 15%. That's why, in general, it is advantageous for non-US investors to use Ireland-domiciled ETFs, as explained nicely in the bogleheads wiki. Japan is one of the rare cases where this is not true, at least for US stocks (see this table), because the Japan/US treaty is at only 10%. However, I am investing in globally diversified ETFs where the US has only a weight of ~60%, so the Ireland ETFs might still be better (because the US will withhold taxes on distributions from the 40% non-US securities hold by the ETF, while Ireland will not). In any case, even for non-US investors in Japan, Ireland-domiciled ETFs are a reasonable choice.

OK, I made some assumptions. So it turns out my assumptions weren't entirely appropriate to your situation

I am not yet a Permanent Resident For Tax Purposes, but will be next year.

So, until you pass the 5 year anniversary, you do not need to pay taxes on any gains or dividends outside of Japan. So, no taxes on those Ireland-domiciled ETFs payable in Japan.
As for income, you only have to pay Japanese Income Tax on the Income derived directly from activities and services performed in Japan, whether the income is remitted to Japan or not. Any income derived from activities and services not performed in Japan are not subject to Japanese Income Taxes unless the funds are remitted to Japan.

This will all change after your 5 year anniversary.

If the Ireland ETF is invested in the US, the US will withhold Dividend Taxes on Dividends paid by the US Stocks, etc..
If you receive the I-94 Notification of Tax Withheld in the March/April timeframe, then you are seeing taxes withheld, and you need to check the rate of Tax withheld.
US Withholding on Dividends is 30% unless you qualify under a Tax Treaty with the US, for which you will have to file a W8-BEN Form in the US.

See US Taxes:
https://www.irs.gov/individuals/interna ... aty-tables
https://www.irs.gov/businesses/internat ... ies-a-to-z
https://www.irs.gov/pub/irs-utl/Tax_Tre ... 19_Feb.pdf

See
https://www.irs.gov/pub/irs-trty/ireland.pdf
Article 10 (Page 14)
Residents of Ireland will be subject to 15% Withholding in the US.

See
https://www.treasury.gov/resource-cente ... treaty.pdf
Article 10 (Page 15)
Residents of Japan will be subject to 10% Withholding in the US.

So in this case it is better to be resident of Japan than Ireland for Tax Purposes.

If you are still resident in Japan next year, and you intend your Tax Domicile to be in Japan (complicated..), and you are receiving an I-94 Notification of Taxes Withheld, you can file a W8-BEN and claim a Japan Withholding Tax rate of 10% on Dividends paid by US enterprises in the US.

See Japan Taxes
https://taxsummaries.pwc.com/japan/indi ... x-treaties
Japan has a Tax Treaty with the Republic Of Ireland and the UK.
https://www.irs.gov/businesses/internat ... -documents
https://www.nta.go.jp/english/taxes/ind ... /12006.htm

See Article 4

4 Tax convention between Japan and your country of residence

　Japan and your country of residence may conclude a tax treaty to avoid double taxation, etc.
With this tax treaty, you may claim the benefits of reducing the tax rate or an exemption from the tax on income such as interest, dividends, royalties or salaries.
　The provisions are different depending on each tax treaty, therefore, you need to refer to each tax treaty in each case.

<DP - The rest of the paragraph is for non-residents in Japan seeking the benefits of the treaty against Japan Taxes. Instead you would need to investigate how to invoke the terms of the treaty in Ireland to claim reduced rates of tax withholding in Ireland.
You invoke the US-Japan treaty in US to claim reduced rates of tax withholding in US by submitting the W8-BEN to the Broker.>

If there are no taxes payable in Ireland on dividends received in Ireland, then as a Permanent Resident for Tax Purposes, next year, you will be subject to the full Japanese Tax on Dividends - National 15% and Reconstruction 0.315% payable in April following the end of the Tax Year, and Resident's Tax 5% payable from July following the end of the Tax Year through to June of the following year - with no application of any Overseas Tax Credit.
This is a Flat Rate of total of 20.315% on Dividend Income over the Dividend Tax Allowance Threshold. There is no greater tax level on Dividend Income.

The 30%, 33%, 43% Japan marginal tax rates only apply to Salary income. Not Dividend Income.

In Japan they can go back 5 years, but that would only apply after you have been a Permanent Resident for Tax Purposes for more than 5 years...

They can audit you back 5 years, and you can go back and file or amend a tax return to claim up to 3 years back.


Therefore, as a non-US Citizen Resident In Japan for Tax Purposes, if you pay 10% withholding on Dividend Income in the US, you will declare the US Dividend income Gross on your Japanese Tax Return, and pay 15.315% National & Reconstruction Tax on the Net after the Dividend Tax Allowance Threshold
After receiving your I-94 Notice of Taxes Withheld, you will go back and claim the Foreign Tax Credit for the 10% Withheld in the US.
They will give you a refund of the 10%, meaning that you paid 5.315% National & Reconstruction Tax.
They will then report the Dividend income to the ToDoFuKen KuShiChoSon and you will be taxed a flat 5% Resident's Tax in the period from July to June of the following year.

[Tkydon]

I went through to confirm the Intricate Detail of Dividend Taxation in Japan.

You can select one of three methods for Taxation of Dividends:

1. For Dividends paid on Japanese Securities by Japanese Entities through Japanese Brokers, Tax will be withheld at 20% + Reconstruction Tax 0.315%. Since this is the Dividend Tax Rate, you would not need to file a Tax Return. You will receive a Gensenchosu 源泉徴収票 From the Japanese Broker. You cannot use this for Foreign Stocks as no Japanese Tax will have been withheld.

or

You can File a Year End Tax Return (Kakutei Shinkoku 確定申告).
For Dividends paid on Japanese Securities by Japanese Entities through Japanese Brokers, Tax will be withheld at 20.315% (15% National, 5% Residential, and 0.315% Reconstruction Tax). You will receive a Gensenchosu 源泉徴収票 From the Japanese Broker, which you will enter into the Kakutei Shinkoku 確定申告 for credit.

You can choose to File either 2. or 3. below. See the Benefit Analysis Below (2.1)


2. Aggregate Taxation - Form-B Pages 1&2

or

3. Separate Self Assessment Taxation - Form-B Pages 1&2 & Page 3


2. Aggregate Taxation - Form-B Pages 1&2
2.1 You would file your Gensenchosu 源泉徴収票 Dividends and they would be taxed at your Marginal Tax Rate, but for qualified Japanese instruments you can claim a Dividend Credit (Page 1- Item 36)
For total Dividends under Y10M the Dividend Credit is 10%, and for any Dividends exceeding Y10M, the Dividend Credit is 5%.

(it doesn't like tabs...)

Marginal Rate --- National (+ve) --- Residential --- Total (Approx) --- Plus Reconstruction Tax
5% ---- 5-10 = 0% --- 0% --- 0%
10% --- 10-10 = 0% --- 0% --- 0%
20% --- 20-10 = 10% --- 10x10/20 = 5% --- 15%
23% --- 23-10 = 13% --- 10x13/23 = 5.6% --- 18.6% (Less than 20%)
33% --- 33-10 = 23% --- 10x23/33 = 6.7% --- 29.7% (More than 20%)
40% --- 40-10 = 30% --- 10x32/40 = 7.5% --- 37.5%
45% --- 45-10 = 35% --- 10x35/45 = 8% --- 43%

As you can see, if you are a Retiree with very little income and your total Taxable Income including the Dividends is somewhere between Y6.95M and Y9M then it would be better to opt for Aggregate Taxation. If over about Y8M, then it would be better to opt for Separate Self Assessment Taxation.

However, Dividend Tax Credit cannot be used for Foreign Dividends and non-qualified Dividends, so the numbers would not be so good.

Marginal Rate --- National --- Residential --- Total (Approx) --- plus Reconstruction Tax
5% --- 5% --- 10% --- 15%
10% --- 10% --- 10% --- 20% (Less than 20%)
20% --- 20% --- 10% --- 30% (More than 20%)
23% --- 23% --- 10% --- 33%
33% --- 33% --- 10% --- 43%
40% --- 40% --- 10% --- 50%
45% --- 45% --- 10% --- 55%

As you can see, if you are a Retiree with very little income and your total Taxable Income including the Dividends is somewhere between Y3.3M and Y6.95M then it would probably be better to opt for Aggregate Taxation. If over about Y6M, then it would be better to opt for Separate Self Assessment Taxation.
Against this, you can take a Foreign Tax Credit for Foreign Taxes Withheld at Source. You should receive a Notification Of Taxes Withheld from your Foreign Broker, such as a US Form 1042-S. See Tax Treaties below.

Otherwise, it is better to opt for 3. Separate Self Assessment Taxation for Dividends

National --- Residential --- Total
15% --- 5% --- 20% --- plus Reconstruction Tax 0.315%

As you can see, if you are a Retiree with income other than this Dividend Income of more than a little over Y3.3M, then this is the more tax effective option.
Against this, you can claim the Tax Credit for the Japanese Taxes withheld (Gensenchosu 源泉徴収票 From the Japanese Broker) and take a Foreign Tax Credit for Foreign Taxes Withheld at Source. You should receive a Notification Of Taxes Withheld from your Foreign Broker, such as a US Form 1099-DIV. See Tax Treaties below.

These numbers are approximate assuming the Dividend Income does not cause you to move up a tax bracket. You would have to do the exact calculation for your balance of non-Dividend Income and Dividend Income.

Once you have selected the Aggregate or Separate Self Assessment Taxation method for a particular year, you cannot go back and change it in a filing ammendment.


Tax Treaties

On Foreign Tax Credit for Foreign Taxes Withheld at Source.

Local Taxation Rules will vary according to Jurisdiction.
The Standard rate of Withholding in the US is 30%.
Yes, If your dividends are earned in the US you are subject to 30% US Tax on those US Earnings..

Dividends may be taxed at source by Withholding in the country where they are paid.
It may be possible to reduce the rate of Withholding Tax if there is a Tax Treaty existing between that country and your country of residence.
e.g. between US and Japan. The Standard rate of Withholding in the US is 30%.
However, Under Article 10, Paragraph 2 (b) of the US-Japan Tax Treaty you can claim a reduced Withholding rate on Dividend Income of 10% in the US. This tax is paid to the US government.
The US-Ireland Tax Treaty allows Irish residents to reduce their US Withholding rate to 15% in the US.
Tax Treaties exist between many nations and you should check on government websites for those countries.

If you have US securities and they are subject to Withholding Tax in the US, you should receive a For I-94 Statement Of Taxes Withheld from your Broker before April 15th.. This is the US equivalent of Gensenchosu 源泉徴収票.

If you file a W8-BEN claiming the reduced rate of Withholding on Dividends under the relevant Tax Treaty, they will reduce the rate withheld.
You can use this 1042-S as proof of Foreign Taxes paid, and claim a Foreign Tax Credit (Page 1 - Item 46)

Unfortunately it arrives too late for the Japan Filing Deadline of March 14th., so unless you can download it directly from your Broker's website, you will have to submit your Japanese Taxes with the Dividend Gross Value, and then go back and amend the Form, and enter Page 1 - Item 46 - Foreign Tax Credit after you receive the documents from your broker.

[rasselbiluga]

Thanks again for the answers guys! Incredible details Tkydon
I have another naive question. I still don't really understand why the US-Japan tax treaty is relevant for Ireland-domiciled ETFs. In my mind, I had the following picture:

1. Assume the ETF holds US stocks. A US company pays dividends to the ETF. 15% tax is withhold, according to the Ireland-Japan tax treaty.
2. The ETF pays out the dividends to the ETF holders (or reinvests in the case of accumulating ETFs). No tax is withhold because the ETF is domiciled in Ireland.
3. Since no tax was withhold in Ireland, as a Japan resident I pay the full 20% tax on the dividends to the Japanese government.

So the US already withhold 15% tax. Still I can invoke the Japan-US treaty? Isn't holding an Ireland-domiciled ETF kind of the same thing as holding stocks from an Irish company?
Also, if the ETF is globally diversified, does that mean that one can (in theory) invoke tax treaties with all the countries from which the ETF holds stocks?

In any case, the point of choosing accumulating ETFs was to avoid filing a Japanese tax return altogether. So either I can verify that indeed no Japanese tax is due on those, or I might consider investing in Japan only (with the risk that I have to sell everything if I leave Japan). The third option would be to choose distributing ETFs, which would mean I need to file a tax return.