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Invoice Tax Breakdown Calculator
Split any invoice into subtotal, tax, and total, per line item.
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About Invoice Tax Breakdown Calculator
Enter line items and a tax rate to see the taxable total, tax amount, and grand total broken down for an invoice.
How invoice tax math works
Each line item is multiplied by its quantity to get the extended price, the taxable lines are summed into a subtotal, and the tax rate is applied once to that subtotal. Tax equals subtotal times rate, and the grand total equals subtotal plus tax. Rounding happens once at the end so the total matches what accounting software expects.
Tax-exclusive versus tax-inclusive invoices
In most US states and B2B invoicing, tax is added on top of the subtotal (tax-exclusive). In the UK, EU, and Australia, displayed prices usually already include VAT or GST (tax-inclusive), so the tax portion is backed out by dividing by one plus the rate. This calculator works tax-exclusive: enter net amounts and it adds the tax for you.
📐 Methodology & Reference Accuracy:
Calculations, formulas, and conversions execute locally in your web browser. Output models are benchmarked against official reference standards and updated for 2026.
🔒 This tool runs entirely in your browser. Nothing is uploaded or stored.
Background reading: Invoice Tax Breakdown on Wikipedia. More: all calculators.
Frequently Asked Questions about Invoice Tax Breakdown Calculator
What is the formula for invoice tax?
Tax equals the taxable subtotal multiplied by the tax rate, and the grand total equals subtotal plus tax. For example, a 500 subtotal at 8 percent gives 40 tax and a 540 total.
Should tax apply before or after discounts?
In most jurisdictions tax applies to the discounted (net) amount, so enter line prices after discounts. If your region taxes the pre-discount price, enter the original prices instead.
How do I handle multiple tax rates on one invoice?
Group line items by rate and run each group separately, then add the subtotals and tax amounts together. Mixing rates in a single calculation produces the wrong total.
Why does my total differ by a cent from accounting software?
Per-line rounding versus end-of-invoice rounding causes one-cent differences. This calculator rounds once at the end, which matches most invoicing standards.
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