Pay previous years tax

I have been trying to fill out and pay my capital gains tax self assessment for the last 6 months. I have called several numbers and used the online help to no avail. I saw somewhere there was mention that I might need to request the self assessment form for the previous year in question (last year 21/22) I cannot find anywhere to request this or change my current setting from filing this years to previous years. Please could you guide me or link me to how I can request self assessment for a previous year?

Hi,

If you contact our Self Assessment department using 'Ask HMRC Online' and request to speak to an adviser we will be able to update this for you. Once we request the return it will update online within 72 hours.

Self Assessment: general enquiries

Thank you.