This situation often involves someone who pays $10,000 in estimated tax while keeping a balance of $100,000 in their checking account that earns less than 1% interest.  Give them one voucher to pay all of their estimated tax in April, and tell them not to worry about it for the rest of the year.  As an alternative, what income do they have that can be a source for withholding? Probably Social Security, and although I don't recommend it because it's too difficult to change, that could eliminate the need for estimated tax payments.