The code identifying the exposure type or collateral reason in the user header of the message (block 3) must be identical to the code contained in field :22H::COLA//xxxx (Exposure Type Indicator) in sequence A of the message content (text block 4).
A collateral substitution can be sent:
by the taker to request the substitution of collateral held, the giver will then send a response confirming its agreement or disagreement
by the giver to propose the substitution of collateral held, the taker will then send a response confirming its agreement or disagreement.