MODULUS 10

Modulus 10 calculations detect single transpositions and incorrect keying of a single digit. The calculation is performed as follows:

The units position and every alternate position of the basic number is multiplied by 2.
The digits resulting from the multiplication are added to those that were not multiplied.
The total is subtracted from the next higher number ending with zero. The result is the check digit.

Assume a basic number	`9 6 4 3 8`
Unit and every alternate	`9 4 8`
Multiplied by 2	`18 8 16`
Digits not multiplied	`6 3`
Add them together	`1+8+6+8+3+1+6 = 33`
Next higher number ending in zero	`40`
Subtract sum of digits	`-33`
Check digit =	`7`
The base number with check digit	`96438``7`

Technical documentation