Calculate sales tax from a pre-tax amount or work backward from a tax-inclusive total.
To calculate sales tax, multiply the amount before tax by the applicable sales tax rate.
$1,000 × 8% = $80 sales tax
$1,000 + $80 = $1,080 total
If the total already includes sales tax, divide the total by 1 plus the tax rate. Do not subtract the tax percentage from the inclusive total.
$1,080 ÷ 1.08 = $1,000 before tax
$1,080 − $1,000 = $80 sales tax
Adding sales tax
Sales tax = Amount before tax × Tax rate
Total = Amount before tax + Sales tax
Removing sales tax
Amount before tax = Tax-inclusive total ÷ (1 + Tax rate)
Sales tax = Tax-inclusive total − Amount before tax
Before tax means sales tax has not yet been added. After tax means sales tax is included in the displayed total.
$100 before 8% sales tax becomes $108 after tax.
A $100 price with 8% sales tax becomes $108. Subtracting 8% of $108 gives $99.36, which is not the original $100 price.
Instead: $108 ÷ 1.08 = $100.
An invoice with sales tax can show the subtotal before tax, the sales tax rate, the sales tax amount, and the total including tax. In the Invoice Generator, tax is a document-level percentage you enter after discounts. The generator does not decide whether an item is taxable or which rate applies.
Check a full invoice total in the Invoice Calculator, or see Creating Invoices for a walkthrough.
Sales tax, VAT, and GST are different tax systems, even though each can change the total amount charged. Use this calculator for a user-entered sales tax rate, the VAT Calculator when you need to add or remove VAT, and the GST Calculator when you need to add GST or extract GST from an inclusive price.