HMRC thought I received a salary for my "Director" role last year, but I didn't

Le posteur a reçu une fausse déclaration de salaire de la part de l'HMRC et doit corriger cette erreur pour éviter de payer trop d'impôts.

Long story short, my dad has "employed" me as a Director of his small business for a few years now. I believe he initially employed me at the suggestion of his accountant, so that he could pay me up to my personal allowance while I was a student and while I didn't have any other form of income. I say "employed" because I only did small things for him from time to time (like working on his website, which hasn't required much maintenance since), rather than working regularly. However, since the last financial tax year, I have been employed full time in another job (after graduating from uni), and have ceased my activities for my dad's business, and he has ceased paying me too (he anticipated that I would get a job so stopped paying me from April 2024). The issue is, HMRC thinks I was on a £12,570 salary from my dad last tax year, even though I received no money from him. Consequently, I have been taxed on all my income from my employer, effectively receiving no personal allowance, meaning I have paid too much tax. I unfortunately only realised this after checking the gov website last week. I presume I need to file for a tax reclaim, but is there anything else I could or should do? Do I need to do anything special to notify HMRC that my listed salary last year was incorrect? Is there anything my Dad or his accountant needs to do? As of right now, I have updated this year's Director salary to £0, but it seems I can't retroactively update last year's salary in the same way. Thanks!