Get sub consultant agreement on tender documents.
When you are bidding for a tender and you are getting prices from sub consultants, make sure the sub gets a copy of the tender documents and agrees with them (or the relevant section) in writing before submitting them and their price to the client.
It is important that the agreement is in writing.
If you don’t get this agreement, the sub consultant may change their prices or conditions once they see the details of the tender.