Six digits, three parts: what is being done, which account it comes from, which it goes to.
| Code | Meaning |
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| Code | Meaning |
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DE3 is six digits. The first two are the transaction type (purchase, cash withdrawal, refund, balance inquiry…), the middle two the from-account type, and the last two the to-account type. When only one account is involved the last four are usually 00; transfers are where both halves carry a value.
The processing code decides which billing and interest rules apply. The clearest case is 01, cash withdrawal: it follows entirely different accounting from 00 purchase — cash advances typically have no interest-free period, with interest accruing from the day of the withdrawal, plus a cash advance fee. When a cardholder asks why they are being charged interest before the due date, the answer is usually that the transaction carried processing code 01, not 00.
The values above are the common ground. Card networks and issuing platforms layer private codes on top, and the same value can mean different things on different networks. For a live integration the counterparty's specification wins; use this table to orient yourself quickly.