Invoice Calculator

Calculate invoice totals with line items, tax, discount, and payment terms.

By Konstantin Iakovlev · Updated September 2026 · Source: SBA — Business Guide

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%
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Discount Type

Subtotal

$100.00

Total Due

$108.25

Line Items

Service or product (1 x $100.00)$100.00

Invoice Summary

Subtotal$100.00
Tax (8.25%)$8.25
Total Due$108.25
Due DateNovember 7, 2026

Use the Invoice Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Accurate billing depends on getting every total right for the goods or services you delivered. Handling line items, sales tax, discounts and payment terms cleanly is what keeps cash flow steady and client relationships intact.

Calculation runs in a set order. Each Line Item Total comes from Quantity times Unit Price, and those totals are summed into a subtotal. Any Discount, whether a percentage or a flat dollar amount, comes off that subtotal next. Tax is then figured on the discounted subtotal and added to it to reach the Total Due, and the due date is today's date plus the Net 15, 30 or 60 terms you pick. There is no separate shipping field: if you bill shipping, enter it as its own line item, and the tool will discount and tax it like every other line, which may not match your state's rules for shipping charges.

Verify the tax rate every time, since rates swing widely by state and locality; California's statewide rate is 7.25%, and local district taxes of 0.10% to 2.00% each (some areas have more than one) come on top of it. Applying a discount on the wrong side of tax is an easy slip that leads to under- or overcharging. State payment terms plainly as well, such as Net 30 or Due on Receipt, to head off delays in collection.

Example: Web Development Project Invoice

  1. 1 Input: two line items, 20 hours of Web Design at $95/hour and 10 hours of SEO Consultation at $120/hour. Discount: 5% for early booking. Sales tax: 6.8% (a hypothetical combined state and local rate). Payment terms: Net 15.
  2. 2 Line items and subtotal: (20 × $95) + (10 × $120) = $1,900 + $1,200 = $3,100.
  3. 3 Discount: $3,100 × 0.05 = $155, leaving $2,945. Tax: $2,945 × 0.068 = $200.26.
  4. 4 Total Due: $2,945 + $200.26 = $3,145.26, payable within 15 days of the invoice date.

Source: SBA — Business Guide · Last updated: September 2026

Frequently Asked Questions

What should a professional invoice include?
Essential elements: your business name and contact info, client name and address, unique invoice number, date issued and payment due date, itemized list of services/products with quantities and rates, subtotal, tax, total due, and payment terms.
What are standard invoice payment terms?
Common terms: Net 30 (due in 30 days, the most common), Net 15, Net 60, Due on Receipt (immediately), and 2/10 Net 30 (2% discount if paid within 10 days). Freelancers often use Net 15 or Due on Receipt.
How do I handle sales tax on invoices?
List the subtotal first, then add applicable sales tax as a separate line item showing the rate and amount. Some services may be exempt from sales tax depending on your state. Always include your sales tax permit number if required by your state.

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