See the main fields and routines involved in calculation:
Customer File
The field Withholding Agent must be 1 – Yes.
TIO File
The fields Sum in Bill and Sum in Invoice must be filled out with 2 to consider VAT withholding value in the bill and to discount it in the invoice, respectively.
Tax File
Rate of 10%
VAT Withholding
To calculate VAT withholding, VAT must be in TIO in a previous sequence and its value must be higher than zero. Besides, a minimum value that is bound to this tax in the option Tax Withholding must be registered. If the item total, added to freight and expenses, is lower than this value, tax is not calculated.