If you get a 1099NEC you would have to fill out your own schedule C for self employment. Then you pay Self Employment tax on your net profit. The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare (FICA). 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. It is on the 1040 Schedule 2 line 4 which goes to 1040 line 23. The SE tax is in addition to your regular income tax on the net profit.
If you are not an employee and get a W2 you need to send in quarterly estimated tax payments to cover any regular tax and SE tax.
The 1040ES quarterly estimates are due April 18, June 15, Sept 15 and Jan 16, 2024. Your state will also have their own estimate forms.
How to make the Estimated payments
https://ttlc.intuit.com/community/tax-payments/help/how-do-i-make-estimated-tax-payments/00/25875
Here are the blank Estimates and instructions…..
https://www.irs.gov/pub/irs-pdf/f1040es.pdf
Or you can pay on the IRS website. Be sure to pick 2023 1040ES payment
https://www.irs.gov/payments
