Can one use past losses, despite "Losses available to be carried forward" field left empty?

Can one use previously declared losses, despite having left the "Losses available to be carried forward" field empty? My employer pays part of my compensation in stock. Income tax is withheld based on their market value when I get them, and then I'm liable for CGT for price changes until I sell them. I normally sell these stocks soon after I get them, but because stock prices fluctuate a lot from day to day, some years I get a few hundred pounds gain, some years a few hundred pounds loss. I always filled the CGT section, and declared gain/losses in the year, but I neglected to fill in the "Losses available to be carried forward" field (out of ignorance.) Now that the CGT allowance is shrinking, I realized that I should perhaps have been more careful and should had filled in the "Losses available to be carried forward" field every year with the cumulative figure off all losses to that year. Can I still carry losses declared in previous years forward? Or is it too late because I left the "Losses available to be carried forward" field empty? Thanks,

Hi Constant Painting,
As long as you have notified HMRC of the losses, we can check to make sure they have not been used. you can then use them or continue to update the return to show losses to carry forward.
Thank you.
 

Thank you!