Does anyone know how family tax credit works?

[RacingSnake]

Hi. I wonder if someone can tell me the answer to this.
We get family credit - not much, just a couple of hundred pounds a year. I have the possibility of earning £500 extra doing some tutoring this year. What I wonder is, will I lose the family tax credit pound for pound? If so, what with paying for my petrol, lunches, etc, I would actually be worse off and it would be silly to take the work
Has anyone any experience of this?

CTC Withdraws at a rate of 39%, so £500 earnings would lose you £195 in CTC, leaving you £305 better off overall, before petrol, lunches, etc.

Thanks. I didn't realize it was possible to know the figure that accurately!

Everything you wanted to know and more!

Gosh! I see the withdrawal rate - thanks - but the rest of it No wonder no-one quite understands it!