Invoice Total Calculator (Discount, Tax & Shipping)
Build a client invoice total from a subtotal by applying an early-payment or volume discount, adding sales tax or VAT, and including a shipping or handling fee.
Last updated: May 2026
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About this calculator
An invoice total layers adjustments in the order they legally apply. First the discount reduces the taxable base: discounted subtotal = subtotal x (1 - discountPercent / 100). Tax or VAT is then charged on that discounted amount, multiplying it by (1 + taxRatePercent / 100), because most jurisdictions tax the net-of-discount price rather than the list price. Finally a flat shipping or handling fee is added after tax in this model. The combined formula is subtotal x (1 - discountPercent / 100) x (1 + taxRatePercent / 100) + shippingFee. Applying the discount before tax matters: discounting after tax would overcharge the customer and misstate the tax owed.
How to use
Take a $2,000 subtotal with a 10% loyalty discount, 8% sales tax, and a $50 shipping fee. The discount brings the taxable amount to $2,000 x 0.90 = $1,800. Tax of 8% raises it to $1,800 x 1.08 = $1,944. Adding $50 shipping gives an invoice total of $1,994. Change the discount, tax rate, or shipping to match your invoice.
Frequently asked questions
Should I apply a discount before or after tax on an invoice?
Apply the discount first, then calculate tax on the discounted amount. In most tax jurisdictions sales tax and VAT are charged on the actual price the customer pays after any discount, not the original list price. Taxing first and discounting afterward would overstate the tax and could put you out of compliance, which is why this calculator reduces the subtotal by the discount before applying the tax rate.
Is shipping taxable on an invoice?
It varies by jurisdiction: some tax shipping when it is part of a taxable sale, others exempt separately stated delivery charges. This calculator adds shipping after tax, treating it as a non-taxed pass-through fee, which is the common case for separately listed freight. If your local rules tax shipping, fold the shipping amount into the subtotal instead so it is included in the taxed base.
How do I calculate VAT on a discounted invoice?
Multiply the post-discount subtotal by the VAT rate expressed as a decimal, then add it back. For a $1,800 net amount at 8% VAT, the VAT is $144 and the VAT-inclusive figure is $1,944. Because VAT applies to the discounted price, granting a discount also reduces the tax collected, so the customer saves both the discount and the tax on that discount, an effect this calculator captures automatically.