How do you calculate an invoice total?

Multiply quantity by rate to get the subtotal, subtract any discount, then apply tax to the discounted amount. Subtotal − discount + tax = invoice total.

Should discount be applied before or after tax?

Before. Tax is charged on what the client actually pays, so apply the discount first and calculate tax on the reduced amount.

Do I charge tax on services?

It depends on your country and, in the US, your state. Many states tax goods but not professional services. Check your local rule before invoicing.

What about late fees?

Add the late fee as a separate line, calculated on the overdue total. A common small-business term is 1.5% per month on unpaid balances.

Invoice Calculator

Work out exactly what to put on an invoice: hours or units × your rate, plus extras, minus a discount, plus tax, minus any deposit already paid.

Quick answerInvoice total = (quantity × rate + extras − discount) + tax on that amount. Example: 10 hours at $75 with 8% tax is a $750 subtotal, $60 tax, and an $810 total.

Your numbers

Edit any field — results update as you type.

Quantity (hours or units)

units

Rate per hour or unit

Extras (materials, expenses)

Discount

Tax / VAT rate

Deposit already paid

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Balance due

$750.00

Invoice total $750.00.

Subtotal

$750.00

Discount

$0.00

Tax

$0.00

Invoice total

$750.00

Put it on the invoice: list the subtotal, discount, and tax as separate lines. Clients query a single number far more often than an itemised one.

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How the invoice total is calculated

Quantity × rate gives the line value. Extras are added, the discount comes off that subtotal, and tax is applied to the discounted amount — never to the pre-discount figure. Any deposit already paid is subtracted last to give the balance due.