That's correct. As @HelenC12 said, it is a pay-as-you-go system.
Most software will assume you earned all your income in a level flow through the year and calculate penalty.
Form 2210 is where you indicate what your quarterly income actually was and then your actual quarterly tax liability can be determined.
Many people think you have to pay 25% per quarter. But if you haven't made the income yet, how can you pay tax that hasn't been earned yet?
The important thing in estimated payments is to not get behind.
Forecast your revenue proactively, set aside income for estimated taxes and make tax deposits and file tax returns on time.
