Is there any penalty for waiting until the end of the year to pay estimated IRS income taxes?
Answers

You can either do it as four equal payments (including any withholding tax) coming to 100% of your total taxes from last year, or you can calculate as you go and file a form 2210 with your taxes next year to show all your quarterly income and the calculations for the tax on that amount and thus that you paid enough. There is a worksheet in Publication 505 for 2019 for making those quarterly calculations.
Paying as you go and filing the 2210 is a lot of numbers to calculate, but you might prefer to do it that way if your income is not in consistent amounts over the year.
If you do not pay enough each quarter by either method, you will be subject to a penalty.

