Assuming you have a Utah state return:
According to the Utah tax agency's website, the State requires a very specific format for the withholding account number:
FYI: Withholding Account Number
The Utah withholding account number is a 14-character number. The first eleven characters are numeric and the last three are “WTH.” Do not enter hyphens. Example: 12345678901WTH.
If form W-2 or 1099 does not include this number, contact the employer or payer to get the correct number to enter on TC-40W, Part 1. Failure to include this number on TC-40W may cause your withholding to be disallowed and delay any refund.
See here for additional information from the Utah State Tax Commission. Check with your employer to verify the number.
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