@yinian - they don't need to be the same, they don't need to be made; they are totally under your control.
the only process you need to go through is pay less (or don't pay at all)! (if you are using the paper vouchers and mailing the payment, just cross through the amount on the pre-printed voucher to match what you are paying).
the only risk is that you under pay and are subject to late penalties in April, but sounds like you have a good control on where you will land in April.,
