Accountants Invoice Total Formula

Learn how to calculate an invoice subtotal, discount, taxable amount, tax and final total.

An invoice total starts with the quantity and unit price, then applies any discount before calculating tax. This order helps separate the amount earned from the tax collected and makes the total due easier to check.

100% Free
No Sign-Up Required
Private & Secure
Mobile Friendly

Invoice total

Invoice total = [Quantity × Unit price × (1 − Discount ÷ 100)] × (1 + Tax rate ÷ 100)

Where:

Multiply the quantity by the pre-tax unit price, reduce that subtotal by the discount, and then add tax to the discounted amount.

Variables Explained

Variable	What It Means	Unit
quantity - Quantity	Number of units, items, hours, or services billed.	number
unitPrice - Unit price	Price charged for each unit before discount and tax.	currency
discountPercent - Discount percentage	Percentage deducted from the subtotal before tax.	percent
taxRate - Tax rate	VAT, GST, sales tax, or other tax percentage applied after the discount.	percent

Step-by-Step Calculation

Calculate the invoice subtotal

The subtotal is the charge for all billed units before any discount or tax.

subtotal = quantity * unitPrice

Calculate the discount amount

Convert the discount percentage to a decimal and multiply it by the subtotal.

discountAmount = subtotal * (discountPercent / 100)

Find the amount before tax

Deduct the discount from the subtotal. This calculator treats the remaining amount as taxable.

taxableAmount = subtotal - discountAmount

Calculate tax

Apply the selected tax rate to the discounted amount.

taxAmount = taxableAmount * (taxRate / 100)

Calculate the final invoice total

Add tax to the amount before tax to find the total amount due.

invoiceTotal = taxableAmount + taxAmount

Worked example: discounted professional services invoice

Quantity10 hours

Unit price$150.00 per hour

Discount10%

Tax rate20%

Calculate subtotal

10 × $150.00

$1,500.00

Calculate discount

$1,500.00 × 10 / 100

$150.00

Calculate amount before tax

$1,500.00 − $150.00

$1,350.00

Calculate tax

$1,350.00 × 20 / 100

$270.00

Calculate invoice total

$1,350.00 + $270.00

$1,620.00

Final Result

The estimated invoice total is $1,620.00, including $270.00 in tax.

Try the Calculator →

Assumptions

✓The unit price is entered before discounts and tax.
✓The same percentage discount applies to the entire subtotal.
✓Tax is calculated after the discount is deducted.
✓One tax rate applies to every billed unit.
✓The currency used for the unit price is the currency of the invoice total.

Limitations

!The calculation does not split items with different tax rates or tax treatments.
!It does not include delivery charges, reimbursable expenses, deposits, credits, prior payments, or withholding amounts.
!Invoice rounding conventions can change the final amount by a small amount.
!Applicable tax rules and invoice requirements can vary by location and transaction type.

Common Mistakes to Avoid

Entering a tax-inclusive unit price when the calculator expects a pre-tax unit price.

Entering 20 as 0.20 for a 20% rate; enter 20 in the percentage field.

Calculating tax from the original subtotal instead of the discounted amount.

Using one combined calculation when invoice lines have different tax rates.

Forgetting to add separate charges or subtract an advance payment outside this calculation.

Related Formulas

Accountants Invoice Total (Hourly) Calculator FormulaCalculate an accountant's invoice total from hourly fees, billable time, expenses and an optional...View formula →Accountants Invoice Total (Daily) Calculator FormulaCalculate an accountant's daily invoice total from billable hours, hourly rate, expenses, discoun...View formula →Accountants Invoice Total (Monthly) Calculator FormulaCalculate a monthly accounting invoice total from your retainer, additional work, expenses, disco...View formula →Accountants Late Payment Interest (Hourly) Calculator FormulaEstimate simple late payment interest on an unpaid accountancy invoice using an annual interest r...View formula →

Frequently Asked Questions

What is the formula for an invoice total with discount and tax?

Multiply quantity by unit price, subtract the percentage discount, then add tax on the discounted amount.

How do I calculate the subtotal on an invoice?

Multiply the number of billed units by the pre-tax price per unit.

Is tax calculated before or after an invoice discount?

This calculator calculates tax after the discount, so the discounted amount is the taxable amount.

How can I calculate a 10% invoice discount?

Multiply the subtotal by 10 / 100. Subtract that discount amount from the subtotal.

Can the formula be used for VAT, GST, or sales tax?

Yes, when a single percentage tax rate applies to the amount being calculated. Enter the relevant rate in the tax field.

Ready to calculate your result?

Use the calculator to get instant results with your own inputs.

Try Accountants Invoice Total→