@Hanpro The people who pay you to babysit are going to claim the money they paid you on their own tax returns. If they are paying you to take care of their children so they can work, they enter the amount they paid to you for the child and dependent care credit on their own tax return. They will want your Social Security number or your Tax ID, because they have to use it to get the tax credit. The amount they pay you and the amount you enter on your own tax return will be cross checked by the IRS. If you do not want to give out your Social Security number then get a Tax ID number from the IRS.
https://www.irs.gov/individuals/international-taxpayers/taxpayer-identification-numbers-tin
**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.**
