Child Benefit, no self assessment, HMRC have issued a bill.

I have been claiming child benefit since Nov 23.

I was just over the 50k earnings at the time. Since the threshold went up I have had a pay rise to just over 60k.

Ive never done a self assessment and was going to get it done but got a message on the HMRC app saying I owe £142. I figured theyve already done the calculation as all my income is PAYE with no savings interest (over the threshold) outside an ISA.

The options are to pay it in a lump sum or adjust my tax code to pay it over the year (£11ish a month).

Am I going to get a fine? Should I have done a self assessment if they have already figured out what I owe and will change my tax code?

Thanks for the help.