Please read all of those links already provided to you VERY thoroughly. Since you did not start this babysitting job until late in the year in 2021, you will not need to file quarterly tax for 2021, but if you continue to babysit in 2022 you should consider sending in quarterly estimated tax payments.
https://ttlc.intuit.com/questions/1901110-do-i-need-to-make-estimated-tax-payments-to-the-irs
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
