ARTICLE 10 CERTIFICATES
Valid certificates for selling a bird are
Specimen Specific
Transaction.
Not sure which one required check it out with DEFRA.
Remember a species on ANNEX B could be placed on 
ANNEX A at any time in the future.
Get a receipt as proof of purchase.
Selling keep a record of the transaction.
You may need confirming evidence should you require
an article 10 in the future.

DEFRA
Department of Environment
Food & Rural Affairs
The Wildlife Licensing
and Registration Service
Zone 1/17 Temple Quay House
2 Temple Square
Temple Quay
Bristol
BS1 6EB
Tele 01173 726290