FA-72818 / Check-digit algorithms / Member archive

Bank-slip mod 11 maps 10 and 11 to zero · case 03

Slips whose remainder is 0 or 1 get verifying digit 0, which is reserved.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Bank-slip style mod-11 verifying digit: nonempty ASCII digits (else None); weights 2,3,...,9 cycle from the rightmost digit; r = 11 - sum mod 11; results 10 and 11 are replaced by 1.

Why this case matters

Payment slip barcodes carry a general verifying digit that banks recompute on capture.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression ["27981996326643088365414819731338534"]	`0`	`1`	Failed

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