Trade Date and Delivery Date

[MyTime]

I have a feeling this question belongs here in the dummies section, but it is something that I have been wondering about recently since I switched from buying ETF to mutual funds.

When I buy a mutual fund in Rakuten, the purchase is logged and there is a "trade date" (約定日), which is the day that I placed the order, and a "delivery date" (受渡日) which is one week after I placed the order.

The money is removed from my balance on the trade date, and the funds are added to my list of holdings within a couple of days.

What I'm wondering is:

When is the price that I pay for the funds fixed? Is it on the trade date? or the date on which the funds are added to my list of holdings?

If the funds are added to my holdings a couple of days before the "delivery date," then what is the significance of the delivery date??

When I am entering the purchase into my accounting software, which of the dates should I enter as the purchase date?

I'm kind of confused about all of this--can anyone enlighten me?

[TokyoWart]

The price you pay and your basis in the security are set on the trade date. You can think of that as the date you have entered a contract with the seller for the security. The security is legally transfered to you on the delivery date (settlement date) which can be important if you are close to an ex-dividend date since a settlement date after that means you miss the dividend. The price you enter in your accounting software for basis is whatever you paid (including any trading commission) as set on the trading date. You track the current value of the security based on whatever the last closing price was so it's likely you already have a small gain or loss by the time you own the position. Note that it's possible to have a failure between the trade date and delivery date either because you don't deliver the money or your counterpart fails to deliver the security, but that shouldn't happen to most retail investors. In the past my Japanese brokerage was willing to wait a few days after trading date before they received the funds but they give me a lower transaction cost now if I have funds in the account to cover the trade when I make it so that is how I make all my trades. The same thing happens in reverse. When you sell a position in Japan you can't actually take the money out of your account until the settlement date but you can usually enter into another trade immediately because it's settlement date will come after the first one.

[MyTime]

I now fully understand. Many thanks indeed TokyoWart!