Thanks for great job, How do i compute WITHHOLDING TAX on the SUBTOTAL AMOUNT or TAX because the withholding tax currently on the invoice is calculated on the invoice total amount. The withholding tax must be computed on the subtotal.
In Australia, I am aware of only one scenario where both GST and withholding tax may be included in a sales invoice. This is where you, as a sub-contractor, have entered into a Voluntary agreement for PAYG withholding by your customer and the customer is not entitled to claim GST credits.
In this case you are correct in that the withholding percentage is calculated on the amount less GST.
It would be interesting to know how this is handled in other tax jurisdictions.
For a workaround, I guess you are already aware that it is possible to toggle the withholding tax setting in the invoice to “Amount” and calculate it manually.
You can also calculate the effective tax withholding rate that gives the correct percentage of withholding when applied to the sum of the subtotal plus tax. In the majority of jurisdictions where withholding tax applies, it is calculated on the total amount of an invoice, including tax. So consult with experts or the revenue authority to be sure your interpretation is correct.