RetireJapan wrote: ↑Sat Feb 24, 2024 5:46 am
I might continue paying into iDeCo at the minimum level to accumulate the tax-free allowance (or do you get that anyway just from having an account?). I believe the monthly fees go up too if you are not paying in.
The Tax Deduction is based on the actual amount of your iDeCo Contributions from Post-Tax Income in that tax year, and your actual Marginal Rate of Income Tax.
Assuming the Marginal Income falls into a single Marginal Income Tax Bracket, then the refund is based on the National Income Tax and Reconstruction Tax Rates (If not you will have to do a calculation for the portion of contributions that fall into each tax bracket).
Marginal Income Tax and Reconstruction Tax rates:
0%, 5.105%, 10.21%, 20.42%, 23.483%, 33.693%, 40.84% or 45.945%...
This means that you are paying the iDeCo contributions out of the remaining income after these tax rates have been applied; the remaining 100%, 94.90%, 89.79%, 79.58%, 76.52%, 66.31%, 59.16%, or 54.06% value after Tax respectively...
If you set that remaining amount to 100%, then the Original Pre-tax Income would be the following multiples of the Post Tax Annual Contribution amount respectively:
1 / (1 - National Income Tax and Reconstruction Tax Rates)
= 1 / Remaining % after Taxes
100%, 105.38%, 111.37%, 125.66%, 130.69%, 150.81%, 169.03% or 185.00%...
The Refund at year end will then be the excess over 100%. i.e. the amount that was paid in tax on that income that should not have been paid.
(1 / (1-Marginal Tax Rate)) -1 x Total Annual iDeCo Contributions
0%, 5.38%, 11.37%, 25.66%, 30.69%, 50.81%, 69.03% or 85.00% of the Contributions, respectively.
Not only that, but you will also then see a reduction in your Total Taxable Income for the Year equivalent to
100% (no reduction on No Taxable Income), 105.38%, 111.37%, 125.66%, 130.69%, 150.81%, 169.03% or 185.00%...
of the Contributions, which in turn will lead to a reduction of 10% of that amount in your Residents' Taxes, and around 12% in your Annual Health Insurance Premiums. (Not a refund in your hand, but a cost saving nonetheless).
(1 / (1-Marginal Tax Rate)) x Total Annual iDeCo Contributions x 10%
0%, 10.538%, 11.137%, 12.566%, 13.069%, 15,081%, 16,903% or 18.5% of the actual contributions in Residents' Tax Reduction
and
(1 / (1-Marginal Tax Rate)) x Total Annual iDeCo Contributions x about 12%
0%, 12.6456%, 13.3644%, 15.0792%, 15.6828%, 0%, 0%, 0% of the actual contributions in Health Insurance Premium reduction for the lower tax brackets, after which you would have already reached the maximum annual Household Health Insurance Premium and would not benefit from any reduction...
Maximum annual Household National Health Insurance Premium = Basic Medical Max ¥650,000 + Latter Day Care Max ¥220,000 + Long-Term Nursing Care Max ¥170,000 = Total Max ¥1,040,000, so top out somewhere between ¥8M and ¥10M Total Household Taxable Income, depending on the number of people in your household.