The Terms and Conditions of the 2023 Basic Income Support for Sustainability (BISS) and other area-based schemes specifically covers the situation where there are no fences or physical boundaries present for reference parcels, as can be found in areas of upland.
"In circumstances where there is no clearly visible physical boundary on the imagery but where a boundary exists on the ground, then other reference sources can be provided by applicants to validate their requests, for example folio maps. This typically will arise in cases of unenclosed lands, particularly commonages, but also callow type land."
Therefore, from a scheme compliance perspective the absence of fencing on commonage lands, where traditionally none have existed, is not deemed a compliance issue nor are there are scheme consequences where livestock subsequently leave the applicants lands due to the lack of fencing once the reference parcel boundary corresponds to a folio boundary or an administrative boundary.