I am trying to create a check digit worksheet for an algorithm where staff
have to use the algorithm hundreds of times daily, so it has to be quick and
efficient.

The algorithm works where the first 12 digits are multiplied and summed
using simple math, and the REMAINDER of the of the sum divided by 9 must
equal the 13th digit.

For example:
My number is 0500450002883, so
1x0=0
2x5=10
3x0=0
4x0=0
5x4=20
6x5=30
7x0=0
8x0=0
9x0=0
10x2=20
11x8=88
12x8=96
where the sum = 264. If you divide 264 by 9, the remaider is 3, the check
digit.

What formula can I use to produce the remaider for 264/9 instead of getting
29.33?