My partner and I have split up, i know i should inform tax credits but he comes to see the children every day and when I have a late shift at hospital he stays with them so that they don't have to get ferried off to all and sundry. We get along well and it's just an unfortunate situation but I do need a bit of extra financial help. iIam worried that if i do tell tax people , they check up and phone or pop round and he is there they will think i am fraudulently claiming.
You must let them know straight away. If you don't and as a result you get more Tax Credit than your entitlement as a single parent, you will eventually have to pay it back - possibly with a penalty as well.
However, if both you and your ex are working it is quite likely your entitlement will go up because both your incomes will have been taken into account when you were together.