Endowment Query

My wife and I took out an endowment policy when we took out a mortgage 24 years ago. Due to a change of circumstances we sold the house some years ago and began renting, we never got round to cancelling the endowment which now matures next year.

Neither of us knows anything about this area but wonder if anyone can tell us whether the payout is taxable and whether it counts as income for the purposes of child tax credit?

Thanks in advance for any help.