I suspect it’s probably because we still have child benefit. I have repeatedly asked them to stop it but apparently it’s only my wife who can do it, and she’s tried on multiple occasions but has been unsuccessful each time.
If you (or someone in your household) claim child benefit and you earn over £50k taxable then you *will* have to complete a return, and give a portion of it back.
There’s no way round this.
If it’s over £60k you have to return it all.
However, there are advantages to doing this. If you lose your job you may get to keep some of the CB. You can’t however go back and claim it retrospectively.
Also the years while claiming CB count towards state pension contributions for you wife AIUI, even if she isn’t working/doesn’t earn enough to count the years.
If you’re bothered about that but don’t want to claim and return the money, you can claim a “zero rate CB” where you get the time counted but get ‘paid’ zero so have zero to repay.