You should pay in quarterly estimated taxes if you don't have enough withholding taken out to cover the tax on all your income. You might be able to increase your W2 withholding, at your part job, to account for the extra income.
You should make estimated tax payments for the current tax year if both of the following apply:
- 1. You expect to owe at least $1,000 in tax for the current tax year, after subtracting your withholding and credits.
- 2. You expect your withholding and credits to be less than the smaller of: 90% of the tax to be shown on your current year’s tax return, or 100% of the tax shown on your prior year’s tax return. (Your prior year tax return must cover all 12 months.)
If your goal is just to avoid the underpayment penalty, then paying 100% of the prior year tax liability is the “safe haven”
2020 TurboTax (TT) can prepare the 2021 quarterly payment vouchers, as described by RayW7, above.
You can use your estimate of your 2021 income, at this point in time. It your self employment income goes up or down, you are allowed to change the later quarter payment to match your actual income.
