How will lump sum affect tax credits?

[MyMorningHasBroken]

Hi, I've been separated for nearly 2 years. I work, get tax credits and childcare and have the 3 children with me. H sent me a lump sum (actually his bonus for this year).
I've talked with an adviser online tonight but he said I need to talk to someone on Tuesday as he wasn't sure.
Anyone had any experience with this?
I put £6000 in a savings account and was planning to pay off bils/debts with the rest.

Ps, I have put the money away for the children, not myself. I'm unsure what his motives were but am fully assuming it's for the children.

As far as I know it makes no difference to tax credits unless you earn more than £300 interest pa. Once things change to universal credit more than £6k will reduce your award.

Would this payment not fall under "child maintenance"?

In which case tax credits don't take it into account.

Would the rest (I kept out to pay bills, childcare ect) been seen as savings too? It's in my current account atm.
I don't know if it would, would he need to specify if it is child maintenance?