Betalinskenmerk

Calculating the check digit for betalingkenmerk is done as follows:

The Accept Giro validation is based on a weighed modulus 11 method, where in a 16-digit payment reference the first position contains the check-digit and the remaining 15 digits contain the actual payment reference code.

The weight:
To every number in the reference a weight is assigned, from right to left these weights are 2, 4, 8, 5, 10, 9, 7, 3, 6, 1 – when the reference contains more then 10 digits these weights are repeated.

The calculation:
A = sum of all products (number * weight)
C = [11 – (modulus 11) A] = check digit
When C = 10 the value 1 is taken
When C = 11 the value 0 is taken

Example:
For example, when the payment reference code is (5)000 0567 8901 2345 (spaces & brackets added for clarification, the 5 is the check digit, 000056789012345 the value):
A = (5*2) + (4*4) + (3*8) + (2*5) + (1*10) + (0*9) + (9*7) + (8*3) + (7*6) + (6*1) + (5*2) + (0*4) + (0*8) + (0*5) + (0*10) = 215
C = 11 – (215%11=6) = 5 (215 divided by 11 = 19 rest 6, 11 minus 6 is 5)

So when looking at the example, the last number in the string is 5, multiplied with the first weight 2 =10; before 5 there is 4, multiplied with the second weight 4 = 16; before 4 there is 3, multiplied with third weight 8 = 24; etc.; after the 10th weight, 11th position from right to left in the string is 5 which has to be multiplied with the first weight 2; before 5 there is 0 which has to be multiplied with the second weight 4; etc.; all results of the multiplications (10+16+24+ … +0+0+0) added up result in 215.