I have daycare receipts and check receipts for sitter I have also paid my sister but no repot or check for babysitting

You can use the amounts you paid your sister to claim the day care credit. Just be sure she knows she has to report the income on her tax return. In the future pay by check to create a paper trail

What if she does not claim the $150 on her income

To claim the day care credit, You have to provide the IRS her SS# and the amount you paid her. If her total  income is so low that she does not need to file a tax return, there's no concern. If she does file a tax return, the IRS computers will catch the missing $150.

Well I have copy of checks where had to pay a friend on weekend I’m going to need friend SSI number.

Yes, if you plan to claim the money you paid him/her for the day care credit.

Is the daycare credit a set amount or depends on how much is paid in

Depends on how much you paid. If you have one kid there is a $3000 limit on what you paid counting. If you have two or more qualifying kids the limit is $6000. The tax credit is somewhere between 20 and 35% of what you paid (up to the $3000/6000). See <a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/f2441.pdf">https://www.irs.gov/pub/irs-pdf/f2441.pdf</a>. It is a non refundable credit (unlike EIC) and can only be used to offset an actual tax liability.