South Carolina Department of Revenue  
Check Digit Calculation - Modulus 10 [2121…]  
Revised 11/29/07 
 
The number is given a weight by which it is multiplied.  The positions in the number are weighted from left 
to right.  The scheme for this routine is 2121… where the first number in the number is multiplied by 2.  
The second number is multiplied by 1 and the third number is multiplied by 2 and so forth.  These weights 
are used to multiply the digits of the number to produce a result.  The result of the multiplication could be a 
two digit number where each digit is treated as a single digit.  An example is 7 x 2 = 14 which will convert 
to 1 + 4.  The last digit (right most) of the grand total of all the multiplication results is subtracted from 10 
to create the check digit. 
 
** If the sum is 10, 20, 30, etc…  the check digit value is 0 ** 
 
Example for File Number: 
File Number = 79098924 
 
Number digits: 7  9  0  9  8  9  2  4 
Multiplier:        2  1  2  1  2  1  2  1 
Results:             14 9  0  9 16 9  4  4  
 
Sum = 1+4+9+0+9+1+6+9+4+4 = 47 
 
Check Digit = 10 – 7 =  3
 
Example for Scan Line with numeric only: 
Column   1         2         3         4         5         6         7         
1234567890123456789012345678901234567890123456789012345678901234567890 
         AAAAAAAAXXBBBBBBBBBXXCCCCCCCCCXXDDEEXXFFFFFFFFFFFXXXXXXXXXXXG 
         30801021  123456789  987654321  1208  00000010000           6 
 
Check Digit calculation for fields B, C, D, E and F using Modulus 10 (21…) starting from the left digit. 
 
Do NOT use spaces in the calculation, only digits (or digit translation from alpha characters). 
 
Number digits: 1  2  3  4  5  6  7  8  9  9  8  7  6  5  4  3  2  1  1  2  0  8  0  0  0  0  0  0  1  0  0  0  0 
Multiplier:        2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2 
Results:             2  2  6  4 10 6 14 8 18 9 16 7 12 5  8  3  4  1  2  2  0  8  0  0  0  0  0  0  2  0  0  0  0    
 
Sum = 
2+2+6+4+1+0+6+1+4+8+1+8+9+1+6+7+1+2+5+8+3+4+1+2+2+0+8+0+0+0+0+0+0+2+0+0+0+0=104 
                    
Check Digit = 10 – 4 =  6
 

South Carolina Department of Revenue  
Check Digit Calculation - Modulus 10 [2121…] (continued) 
Revised 11/29/07 
 
Example 1 for Scan Line with alpha (4 letters in name control field): 
Column   1         2         3         4         5         6         7         
1234567890123456789012345678901234567890123456789012345678901234567890 
         AAAAAAAAXXBBBBBBBBBXXCCCCCCCCCXXDDEEXXFFFFXXGGGGGGGGGGGXXXXXH 
         33321027  123456789  987654321  1207  CLAR  00000010000     7 
 
The alpha translation into numeric for check digit calculation is as follows: A=1, B=2, C=3, D=4, E=5, F=6, 
G=7, H=8, I=9, J=1, K=2, L=3, M=4, N=5, O=6, P=7, Q=8 R=9, S=2, T=3, U=4, V=5, W=6, X=7, Y=8, 
Z=9. 
 
Check Digit calculation for fields B, C, D, E, F and G using Modulus 10 (21…) starting from the left digit. 
 
Do NOT use spaces in the calculation, only digits (or digit translation from alpha characters). 
 
Number digits: 1  2  3  4  5  6  7  8  9  9  8  7  6  5  4  3  2  1  1  2  0  7  C  L  A  R  0  0  0  0  0  0  1  0  0  0  0 
Multiplier:        2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1   2   1  2  1  2  1  2  1  2  1  2  1  2 
Results:             2  2  6  4 10 6 14 8 18 9 16 7 12 5  8  3  4  1  2  2  0  7  6  3   2   9  0  0  0  0  0  0  2  0  0  0  0    
Sum = 
2+2+6+4+1+0+6+1+4+8+1+8+9+1+6+7+1+2+5+8+3+4+1+2+2+0+7+6+3+2+9+0+0+0+0+0+0+2+0+0+0
+0=123                    
 
Check Digit = 10 – 3 = 7 
 
Example 2 for Scan Line with alpha (2 letters in name control field): 
Column   1         2         3         4         5         6         7         
1234567890123456789012345678901234567890123456789012345678901234567890 
         AAAAAAAAXXBBBBBBBBBXXCCCCCCCCCXXDDEEXXFFFFXXGGGGGGGGGGGXXXXXH 
         33321027  123456789  987654321  1207  HO    00000010000     4 
 
The alpha translation into numeric for check digit calculation is as follows: A=1, B=2, C=3, D=4, E=5, F=6, 
G=7, H=8, I=9, J=1, K=2, L=3, M=4, N=5, O=6, P=7, Q=8 R=9, S=2, T=3, U=4, V=5, W=6, X=7, Y=8, 
Z=9. 
 
Check Digit calculation for fields B, C, D, E, F and G using Modulus 10 (21…) starting from the left digit. 
 
Do NOT use spaces in the calculation, only digits (or digit translation from alpha characters). 
 
Number digits: 1  2  3  4  5  6  7  8  9  9  8  7  6  5  4  3  2  1  1  2  0  7  H   O   0  0  0  0  0  0  1  0  0  0  0 
Multiplier:        2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2   1   2  1  2  1  2  1  2  1  2  1  2  
Results:             2  2  6  4 10 6 14 8 18 9 16 7 12 5  8  3  4  1  2  2  0  7 16  6  0  0  0  0  0  0  2  0  0  0  0    
Sum = 
2+2+6+4+1+0+6+1+4+8+1+8+9+1+6+7+1+2+5+8+3+4+1+2+2+0+7+7+6+0+0+0+0+0+0+2+0+0+0+0= 
116                   
 
Check Digit = 10 – 6 = 4 
 

South Carolina Department of Revenue  
Check Digit Calculation - Modulus 10 [2121…] (continued) 
Revised 7/28/08 
 
Example 3 for Scan Line with alpha (3 letters in name control field): 
Column   1         2         3         4         5         6         7         
1234567890123456789012345678901234567890123456789012345678901234567890 
         AAAAAAAAXXBBBBBBBBBXXCCCCCCCCCXXDDEEXXFFFFXXGGGGGGGGGGGXXXXXH 
         33321027  123456789  987654321  1207  POE   00000010000     6 
 
The alpha translation into numeric for check digit calculation is as follows: A=1, B=2, C=3, D=4, E=5, F=6, 
G=7, H=8, I=9, J=1, K=2, L=3, M=4, N=5, O=6, P=7, Q=8 R=9, S=2, T=3, U=4, V=5, W=6, X=7, Y=8, 
Z=9. 
 
Check Digit calculation for fields B, C, D, E, F and G using Modulus 10 (21…) starting from the left digit. 
 
Do NOT use spaces in the calculation, only digits (or digit translation from alpha characters). 
 
Number digits: 1  2  3  4  5  6  7  8  9  9  8  7  6  5  4  3  2  1  1  2  0  7  P    O   E   0  0  0  0  0  0  1  0  0  0  0 
Multiplier:        2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2  1  2   1   2   1  2  1  2  1  2  1  2  1  2  1  
Results:             2  2  6  4 10 6 14 8 18 9 16 7 12 5  8  3  4  1  2  2  0  7 14  6 10  0  0  0  0  0  0  1  0  0  0  0    
Sum = 
2+2+6+4+1+0+6+1+4+8+1+8+9+1+6+7+1+2+5+8+3+4+1+2+2+0+7+1+4+6+1+0+0+0+0+0+0+0+1+0+0
+0+0=114                  
 
Check Digit = 10 – 4 = 6