RetireJapan

I already have a regular NISA but next year I want to go the Tsumitate route as it seems better over the long term. I understand this is more suited for Dollar Cost Averaging and "accumulation" but I would rather just put the whole 400K in one go rather than monthly payments of say 33K. I'm a lump sum guy, not really into DCA.

I'm guessing it's not possible to put in the full 400K in January as it goes against the purpose of Tsumitate? Is there a workaround? E.g. Is it possible to put in 398,900 in January then in the reminding 11 months put in 100 Yen? Many thanks in advance.

Yes, many providers allow you to do this (make a larger 'bonus' payment manually then set the monthly payment to a smaller amount).

I am lazy though so will just set 33,333 a month and forget about it when I switch to tsumitate NISA from 2023

out of interest-why do you think the tsumitate is better over the long term

If you prefer lump sum, then regular NISA is probably the best choice for you. Tsumitate is.... tsumitate by definition