I still don’t understand. If the “anticipation on taxes on revenues” is 20% of the Amount, why is it not 1,040 instead of 1,000? That would make your net 4,160.

Assuming the 1,000 was just a typing error, I think there are a couple approaches.

The first is to create the sales invoice normally, indicating IVA 22% tax code on the taxable line items. Then, apply a withholding tax percentage adjusted to reflect the compound rate. If every line item was subject to IVA 22%, the percentage would be 34.4262%. (This is because withholding tax in Manager is calculated on the sum of Sub-total plus tax-code-applied taxes. But you don’t want the split withholding on the full total, only on the underlying base.) Looking at some equations:

Amount + VAT - VATWithholding - SplitWithholding = Net **OR**

5200 + (.22 * 5200) - (.22 * 5200) - (.20 * 5200) = 4160

(I’m only showing all these interim numbers that cancel out for completeness. Other circumstances might not have them cancelling each other.) Of course, this boils down to:

Amount * (1 - SplitWithholding) = Net **OR**

5200 * (1 - .20) = 5200 * .8 = 4160

So what withholding percentage is required? Let’s call that variable W. A little algebra yields:

W = 1 - (1 - SplitWitholding) / (1 + VAT) = 1 - (.8 / 1.22) = .344262 = 34.4262%

The resulting sales invoice looks like this:

You would probably want to add a note to explain what the withholding tax includes and how it was calculated.

The other way you could do this is to treat the split amount as a zero-tax, negative line item, posted to a suitable asset account. (Since this is not an automatic posting, you cannot use the same *Withholding tax receivable* account.) The problem with that approach is that you are lowering the Total amount, so you would need to enter an artificially high withholding rate for the VAT. It is probably easier to explain the first approach than the second.