Why does my tsumitate-NISA look like this?

[Roger Van Zant]

I pay 33,333 yen each month into a tsumitate-NISA through SBI, 100% into the eMaxis Slim All Country.
I just checked my balances and was surprised to see this:

https://ibb.co/RjN7P1D

There should be 400,000 yen (12 months x 33,333 yen) in my 2021 allocation, yet there is only 366,663 yen.
Also, I have only paid in four months' worth this year (Jan ~ Apr), so the balance should be 33,333 x 4 = 133,332 yen.
However, the balance shows 166,665 yen, so an extra month of 33,333 is already in there.

It seems the missing 33,333 from 2021 has been added to my 2022 balance.

What is going on? Some kind of weird timing issue due to SBI?

Many thanks!

[RetireJapan]

What is the date of your monthly contribution? If it is too late in the month, your December one might not clear in time, and therefore be allocated to January instead. Maybe. That's what happens if you buy something too late in ordinary NISA.

Anyone else?

[Haystack]

We would need to see the page with the purchase/delivery dates. This screen does not give us enough information.

....

Most likely

A. Your Nisa did not start until Feb/March. You set the monthly payment at 333,33. You did not set the bonus to make up for the missing months.

B. This Years NISA actual start Late Dec.2021. Your NISA purchased in late Dec for this years Nisa.

[Roger Van Zant]

What is the date of your monthly contribution? If it is too late in the month, your December one might not clear in time, and therefore be allocated to January instead. Maybe. That's what happens if you buy something too late in ordinary NISA.

Anyone else?

My monthly contribution is always the last day of the month, or as close to it if it is a holiday.
Hmm, maybe that would explain it.

[Roger Van Zant]

We would need to see the page with the purchase/delivery dates. This screen does not give us enough information.

....

Most likely

A. Your Nisa did not start until Feb/March. You set the monthly payment at 333,33. You did not set the bonus to make up for the missing months.

B. This Years NISA actual start Late Dec.2021. Your NISA purchased in late Dec for this years Nisa.

I see.
I did not realize the contribution made at the end of December 2021 would become part of my 2022 NISA as opposed to my 2021 allotment.
It's not a big deal, I guess. I had just not noticed the discrepancy before.

[Haystack]

We would need to see the page with the purchase/delivery dates. This screen does not give us enough information.

....

Most likely

A. Your Nisa did not start until Feb/March. You set the monthly payment at 333,33. You did not set the bonus to make up for the missing months.

B. This Years NISA actual start Late Dec.2021. Your NISA purchased in late Dec for this years Nisa.

I see.
I did not realize the contribution made at the end of December 2021 would become part of my 2022 NISA as opposed to my 2021 allotment.
It's not a big deal, I guess. I had just not noticed the discrepancy before.

It is not intuitive, they publish a schedule and send it out via the broker messaging service. Your fine now obviously, but some will be caught out their first year due to either A or B as described above.