Chaimaine Smith

Hi, I've finally received my pay rise which I was supposed to receive in April (backdated) however it wasn't agreed until October my question is can my employer deduct from my wages for any absences I had taken before the rise was agreed upon? I've had a substantial amount taken but it only seems that they have deducted for only 8 days at the new rate but I have already had one deduction for five of those days in October