If your letter shows you have set-aside entitlements you will have to set-aside a hectare of land for each set-aside entitlement, whether or not you remain in arable crop production. In general, only arable land can be used for set-aside.
Your set-aside entitlements only include the obligatory set-aside element of your AAPS claims from the reference period. Any hectares above this become part of your livestock/arable reference amounts. For example, if you had 90 hectares of cereals and 20 hectares of set-aside then your set-aside obligation was 11 hectares, i.e. 10% of the total claim of 110 hectares. So under SFPS your obligatory set-aside entitlement will be 11 hectares.
The remaining 9 hectares of voluntary set-aside will become part of your livestock/arable reference amounts.
Set-aside entitlements must be claimed each year on the Aid Application. If set-aside entitlements are not claimed, and have not been sold or leased out, then a sanction will apply.
If you sell or lease your set-aside entitlements, the buyer or lessee is obliged to continue the set-aside obligation.