You pay the Self Employment tax on your regular 1040 return you will file in April 2023. So you should make quarterly estimated payments during the year to cover any tax due on it unless you increase any W2 withholding to cover the SE tax. And it's based on your Net Profit on Schedule C, not the total income received.
Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment. You pay 15.3% SE tax on 92.35% of your Net Profit greater than $400. The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare. So you get social security credit for it when you retire. The SE tax is already included in your tax due or reduced your refund. The SE tax is in addition to your regular income tax on the net profit.
Are you worried about paying a penalty for not paying enough in quarterly? If you do not pay in enough tax from withholding and estimates, you may have to pay a penalty for underpayment of estimated tax. Generally, most taxpayers will avoid this penalty if they owe less than $1,000 in tax after subtracting their withholdings and credits, or if they paid at least 90% of the tax for the current year, or 100% of the tax shown on the return for the prior year, whichever is smaller. It is included in your tax due or reduces your refund.
