5250 error 0015: Check digit error

What it means

Account numbers, item numbers and member numbers often end in a check digit worked out from the other digits. If one digit is wrong, or two are swapped, the check digit no longer fits. A programmer can ask for this test on a field with CHECK(M10) or CHECK(M11) in the DDS, for modulus 10 or modulus 11, or with the forms CHECK(M10F) and CHECK(M11F). When the display station finds that the check digit doesn't fit, it locks the keyboard and shows 0015.

The rightmost digit is always the check digit. For modulus 11, IBM's DDS reference describes the method. Each digit of the base number is multiplied by a weight, starting with 2 at the right and rising to 7, then starting again at 2. The products are added, and the remainder after dividing by 11 decides the check digit. Some base numbers give a remainder that has no valid check digit, and IBM tells programmers not to issue those numbers at all.

The two forms differ in timing. With M10F or M11F the number is checked as it is typed into the field. With M10 or M11 it is checked when Enter or a function key is pressed. IBM's 5291 operator guide ties 0015 to the number you have just entered. IBM's DDS reference doesn't say whether a failed check at Enter shows 0015 or a message. A self-check field holds at most 31 digits if it is numeric.

Common causes

• One digit mistyped, often a neighbor on the numeric keypad, such as 4 for 7.
• Two digits swapped, such as 1243 for 1234. Check digits exist to catch this kind of slip.
• A digit left out or typed twice, which moves every digit to a different weight.
• The number belongs to another numbering scheme, for example an old account number from before check digits were added, or a number from another system that uses a different method.
• The number was issued without a valid check digit, for example assigned by hand.

How to find the problem

1. Compare the number on the screen with the source document digit by digit. Look hardest at swapped neighbors.
2. Press Help while 0015 is on the error line to see the system's text for the error.
3. In the display file source, look for CHECK(M10), CHECK(M10F), CHECK(M11) or CHECK(M11F) on the field. That tells you which method applies, so you can work out the expected check digit by hand if a number keeps failing.

How to fix it

• Press Reset (also called Error Reset) to free the keyboard. In many PC emulators Reset is the left Ctrl key by default. Then retype the whole number carefully.
• If a number you are sure of keeps failing, don't try variations until one passes. Report it to whoever looks after the application, with the number, because either the number or the field's method is wrong.
• For programmers, make sure the field uses the same method, modulus 10 or modulus 11, as the system that issues the numbers. A field can't have both, and it can't have both M10 and M10F.
• For programmers, if some valid numbers have no check digit, such as legacy accounts, remove the CHECK and validate in the program, where you can allow the exceptions.
• For programmers, note the restrictions. M10F and M11F can't be used in a file with USRDSPMGT or on a field with CHKMSGID or WRDWRAP, and option indicators aren't allowed on any of the four.

Technical reviewer: Albert Joseph, WND Software.

Last reviewed 2026-10-18 by the WND Software team. Written in our own words. For the full reference, check IBM’s 3270 or 5250 display documentation.