Your business losses can potentially be carried forward indefinitely, that is until the business ceases.
Only the last 2 tax year allow for your tax return to be amended (21/22 & 22/23).
If you submitted your tax return online, you can log into them and amend the carry forward figures.
If you submitted paper returns, you can submit amended supplementary pages.
For the earlier 2 tax years (19/20 & 20/21) you need to submit a letter detailing your loss carry forward changes.
I regret that the tax years earlier than this cannot be amended.
Have a look at :
HS227 Losses (2023)
It has a worksheet to help you keep track of your losses.