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The number itself is 8 or 9 digits, with a check digit.

All values are added together and the remainder of the final value divided by 10 is the check digit.

If the final difference is 10, then the check digit becomes 0.

The 9th position is that of the check digit.

Unlike many similar numbers, no check digit is included.

It is 7 characters in length and contains a check digit.

That result is the check digit, except in the two cases where it is 10 or 11.

Subtract the remainder from 98, and use the result for the two check digits.

Another example: to calculate the check digit for the following food item "01010101010".

In that case, use 0 as the check digit.