Self Assessment Tax Payment

Hi In previous years, I have had to make tax payments to HMRC of £5k plus each year. This year, my income has increased but my self assessment submission calculation is showing that the HMRC now owe me money. Can I just check, is this because the HMRC change individuals tax codes each year/during the year, or is there a potential error on my submission (which I have checked 2-3 times but appears correct)?

Hi 
Unfortunately, it is not possible to check individual tax records through this forum.
If you have a question which relates to your personal tax situation or tax code please contact our helpline:
Income Tax: general enquiries
On this page you will also see a link to personal tax account.
Sign in or set up which may be the quickest way to review information relating to pay and tax history, tax codes and how to change them.
Thank you.