There are some quick ways to do this. Some of the other answers lead you in that direction. Hereu2019s my take on this:If you pay in an amount at least equal to what you paid in last yearu2019s taxes ( the total tax bill), you wonu2019t have a penalty. Yea, you might owe, but no penalty.If you donu2019t pay in, youu2019ll pay what is in essence interest, in the form of a non-deductible penalty. The interest rate is under 5% annualized. But, you will have a humongous tax bill.Maybe you can adjust your W-4, and have large withholding from your salary now, which takes care of most of the estimate. So, if you are married, claim single . It will hurt a bit on each paycheck, but youu2019ll pay in a lot more, maybe covering what you owe.To get an idea of what you owe on the independent contractor earnings, first you have to know what they are! Take what you received, and deduct your expenses. Remember, you may be entitled to an office in home, your mileage, and other easily missed deductions. (A CPA or EA would be a good person to help you this yearu2023 theyu2019ll know how to calculate everything, and itu2019s a lot better than you struggling or guessing). With your net income calculated, you must figure your self employment tax ( at about 15%, and your income tax ( use 12% for fed, 3 - 5 % for most states). Youu2019ll have a ballpark amount. ( I know, the rates are all over the place, I am just throwing you what I think most people end up at. Again, great reason to consult with a CPA or EA.)Kudou2019s to you for being on top of this and not doing what some of my clients do, which is wait until next April and then have a heart attack, despite my pleading!