VCM74040 - Share Loss Relief: individual and corporate claimants: individual claimants: priority over other reliefs for losses
You should check the other guidance available on GOV.UK from HMRC as Brexit updates to those pages are being prioritised before manuals.
If other reliefs are also available to set against income in a particular tax year, Share Loss Relief claimed by individuals is given before either relief in respect of trade losses or relief for losses in the first four years of trade. This is because section 133(4) gives priority to Share Loss Relief over relief under either ITA07/S64 or S72.
For general guidance on prioritisation of losses see BIM75215.