Is 00 the only approval code in ISO 8583?

No. The 1987 table also defines 08 (honour with identification), 10 (approved for partial amount) and 11 (approved, VIP), among others, and ISO 8583:2023 groups every approval into the 0000–0999 action-code range. But 00 is the one you will see for an ordinary approved authorisation, and treating anything in the approval range as success is safer than testing for equality with 00.

Why does my approved transaction still not settle?

Because an authorisation and a capture are different messages. A 00 on a 0100 authorisation holds the funds; the money moves when the matching financial or capture message clears. If approvals are not turning into settlements, look at whether the capture is being sent at all, and whether it carries the same retrieval reference number as the authorisation.

ISO 8583 response code: 00

The issuer approved the transaction. A field 39 of 00 is the only unambiguous success value in ISO 8583 — every other code is a decline, a referral or an error.

Approved or completed successfullyNot an error

This is a success response, not a failure.

What it means

The issuer authorised the amount requested and the funds are held against the cardholder's account. In an authorisation flow this is the response you capture against later; it is not itself a movement of money. Note that an approval says nothing about whether the message you sent was the message you meant to send — an approval for the wrong amount is still an approval.

Common causes

The authorisation succeeded normally.
A partial approval was returned as 00 by an acquirer that does not use the separate partial-approval code, with the approved amount in field 4 differing from what you requested.

How to fix it

Nothing to fix. Record the approval code from field 38 — you will need it to capture, reverse or refund the transaction.
Compare the amount in field 4 of the response against the amount you sent. An acquirer that supports partial approval can approve less than you asked for, and treating that as a full approval under-collects.
Store field 39 as the string "00", not as the number 0. Response codes are two-character alphanumeric and the leading zero is significant.

Tools that help

Frequently asked questions

Is 00 the only approval code in ISO 8583?: No. The 1987 table also defines 08 (honour with identification), 10 (approved for partial amount) and 11 (approved, VIP), among others, and ISO 8583:2023 groups every approval into the 0000–0999 action-code range. But 00 is the one you will see for an ordinary approved authorisation, and treating anything in the approval range as success is safer than testing for equality with 00.
Why does my approved transaction still not settle?: Because an authorisation and a capture are different messages. A 00 on a 0100 authorisation holds the funds; the money moves when the matching financial or capture message clears. If approvals are not turning into settlements, look at whether the capture is being sent at all, and whether it carries the same retrieval reference number as the authorisation.