The MT 303 can only be sent or received over FIN by financial institutions registered with SWIFT in the MT 303 message user group. Should a registered user receive an MT 303 without having a bilateral agreement with the fund manager, the Receiver should query the message according to normal banking practice.
To cancel a previously sent MT 303 and the complete set of instructions (field 22A is CANC), field 21 must contain the reference, ie, the content of field 20, of the message containing the allocation instruction to be cancelled; the cancellation message must contain a copy of at least the mandatory fields of the general information and trade information blocks.
To amend the terms of the block trade and consequently the complete set or a number of individual allocations (field 22A is AMND), field 21 must contain the reference, ie, the content of field 20, of the message containing the allocation instruction to be amended; the amendment message must contain both the unchanged and the changed/new fields of the original instruction, ie, it must contain the general information, trade information and a complete set of new allocation blocks. The amendment message will replace the original message.
To amend a number of individual allocations (field 22A is AMNA): field 21 must contain the reference, ie, the content of field 20, of the message containing the allocations to be amended; the amendment message must contain the mandatory fields of both the general information and trade information blocks. Each individual 'changed' allocation must contain the reference (field 21A) of the allocation which has to be modified. It must also contain both the unchanged and the changed/new fields of the original individual allocation.
While the maximum message length is 10,000 characters, it may occur that more than one MT 303 is needed for the entire set of allocations. In this case additional MT 303s are sent. These MT 303s must contain the same general information and trade information blocks as the first MT 303. Within the allocation details block, the page number will be increased by one compared to the previously sent message.