Do tax credits ask for proof of earnings when you estimate them UK answers only please.?

Question

If you estimate your earnings and then when they ask you what you actually earned, do you have to send proof of what you have said.?

Answer 1

Yes, they are checked against tax office records.

Answer 2

no. because they have access to your p60 with all your earnings on it

Answer 3

they usually send a form to your employer to fill out the last 12 weeks of wages you have recieved

Answer 4

I dont know why they ask you to confirm, they have access anyway.