Anonymous wrote:As long as you pay enough, you'll be fine. They don't go back and see if you paid exactly 25% each quarter. I pay what
I can when I can, usually in two installments, sometimes just one prior to April 15. The only time you pay penalties is if you underpay estimated taxes (and they are minor).
This. The only way they can know when you earned it is if they audit you. When I was self-employed, I usually paid on time each quarter, but some years I skipped a quarter and doubled up on the next. Never had a problem.