Please help - HMRC have not helped

HMRC I am getting really quite stressed now about this and despite making numerous phone calls to HMRC, I still don’t have a clear answer. Please please somebody help me with the below. I earn a modest wage around £30,000 per year, I am not rich by any means and I need some guidance. Through savings and shares I have built up a healthy amount which I’m planning to use next year to pay my mortgage off when my current deal ends. I put £50,000 in a 12 month saver which matured in December 2023 and gained around £2,100 in interest. I completed a 3 year share scheme through my work that ended December 2023 and made around £18,000 profit on this. I moved it in to a stocks and shares ISA and calculated myself (and had it confirmed on the phone by HMRC) that I’d need to pay £145 in capital gains tax. After doing a self assessment return - which I have never done before - I generated a payment reference number and paid this online. When I log in to my HMRC now it says I have a credit of the £145, and an option to return this to my bank. It also says I owe £200. As I said at the start, I am not a financial whizz, and I can’t seem to get any help from HMRC DESPITE me trying my best for 6 months to pay what I owe and make sure I am doing everything correctly and by the book. I also now have £85,000 in a 12 month saver which ends in December and will generate £4,462 interest when it matures. I believe I’ll have to pay around £790 in tax on this too. Please, can anybody help?

Hi ,

As we would need to access your records to review this, you will need to contact our Self Assessment team.

Self Assessment: general enquiries

Thank you.