This applies to Companies
Losses carried forward from 01/04/2017 can be set off against not just trading income, but any other income that the company derives.
However there is a 50% restriction where companies and or groups are carrying forward losses exceeding £5m.
Capital losses are still ring-fenced so that these can only be relived against future capital gains.
Below link gives much more comprehensive information.
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/525929/FINAL_PDF_3.pdf
Further reading from Affinity: