Tax credits and maternity leave

[Pleasedontdrawonyoursister]

I’ve just had my tax credit renewal pack through. All looks ok but then I discovered that I am able to deduct £100 pw of income for any weeks I was on SMT. Problem is I never called them to say I was on mat leave as this is my third child so thought I wasn't entitled to any extra. Am I going to get in trouble for not notifying them? Will they try to back pay me any extra payments for previous year? I’m really cross with myself for not notifying them but it really didn’t cross my mind until the renewal pack turned up .

No just ring now and say last yrs figures were wrong. You were on x amount of weeks. Maternity. They will re calculate.
Just done mine and they owe me. £2600

I called and he said they may fine me for not telling them I had another child uh oh.

But if you haven't told them then you've not had anything additional off them so how can you be fined. Or am I missing something?

I assume because you are meant to let them know of any changes within a certaim period

You do always need to notify them of any changes in circs regardless of whether they will have an effect. I swapped jobs, exactly the same salary, and rang to check if it made any odds - they were adamant every change needed to be passed to them.