Tax withheld

Net payable to supplier
Invoice total including tax
Sales tax on the invoice
Invoice needed for the target net

How it works

Withholding tax — deducted at source, TDS in some jurisdictions — requires the payer to hold back a percentage of an invoice and remit it to the tax authority directly. The supplier receives the balance and claims the withheld amount as credit against their own tax bill.

The gross-up runs the calculation backwards. If a contract promises a specific net amount, the invoice has to be raised at a higher figure so that the net survives the deduction. Dividing by one minus the rate gives that figure; adding the rate does not.

Withheld = taxable × rate · Gross-up = target net ÷ (1 − rate)

  • Taxable base — usually the invoice value excluding sales tax
  • Rate — the withholding percentage for the category of payment
  • Net payable — invoice total less the amount withheld

Worked example

A 250,000 invoice with 18% GST and 10% withholding on the base

Inputs

Invoice base250,000
GST18%
Withholding rate10%

Results

Withheld25,000
Net payable270,000
Invoice total295,000

Withholding is charged on the base, not on the GST-inclusive total — a distinction worth 4,500 on this invoice.

Frequently asked questions

Is withholding calculated on the amount including sales tax?

Usually not. Most regimes apply it to the invoice value excluding GST or VAT, because the tax component is not the supplier’s income. This calculator follows that convention.

What is a gross-up and when do I need one?

When a contract guarantees the supplier a specific net amount. The invoice has to be raised high enough that the promised net survives the deduction — divide the target by one minus the rate.

Does the supplier lose the withheld money?

No. It is credited against their tax liability, so it is a timing difference rather than a cost. It does affect cash flow, which is why suppliers care about the rate applied.

Is my data sent anywhere?

No. The calculation runs entirely in your browser. Nothing you type is transmitted to us or stored.

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