Ask Kilby.

These two SWIFT return codes are pointing at different problems, so let me separate them before getting to the extension.

AM04 is "insufficient funds" — the counterparty's account didn't have enough cash to cover the delivery. That's a liquidity or funding problem on their side, or possibly a booking/allocation mismatch causing the wrong account to be debited.

AC04 is "closed account" — the cash leg is hitting an account that no longer exists. That's an SSI problem. Either your standing settlement instructions are stale, or the counterparty's bank account changed and your records weren't updated.

The AC04 is actually the more urgent fix — a payment routing to a closed account won't settle regardless of how much liquidity exists. You need to get correct cash settlement instructions from the counterparty or their custodian before anything else moves.

On the Reg T Extension:

For a DTC fail on a US equity where you're unable to make delivery due to the settlement break, the applicable reason codes depend on what's actually blocking you:

The most direct fit here is Reason Code 15 (COD-Fail 35 days) — but only if you're at or past the 35th calendar day from trade date. That gives you up to 14 calendar days, does not count toward the 5-extension limit, and is marked final on the transaction.

If you're before T+35, then look at Reason Code 21 (Exceptional Circumstance) — because a failed DTC delivery driven by an SSI/account defect (AC04) and counterparty funding failure (AM04) isn't cleanly covered by the standard codes. Code 21 gives you up to 14 calendar days, does not count toward the 5-extension limit, and is not final, meaning you can come back again if needed. However, it should only be used when no other code squarely fits.

My recommendation: Fix the AC04 SSI problem first — that's your actual blocker. Get updated cash settlement instructions confirmed in writing from the counterparty, correct your SSI record, and retry the cash leg. Meanwhile, file the Reg T extension to protect yourself on the regulatory clock. If you're pre-T+35, Code 21 gives you the most flexibility. If you've crossed T+35, Code 15 is your vehicle.