Service Invoice Template

Each labor row is Hours × Rate; each parts row is Qty × Unit price. The two sections sum into the Subtotal. Tax applies only to the lines you flag taxable — every parts row has its own Taxable? checkbox, and the whole labor section is taxed (or not) by the single Tax labor? toggle:

subtotal     = Σ (hours × rate) + Σ (qty × unit price)
taxable base = (tax labor? Σ labor : 0) + Σ taxable parts
tax          = rate × taxable base, after any discount is applied to those lines
total        = subtotal − discount + tax + trip charge
balance due  = total − amount paid

A discount is applied to the subtotal before tax, and it reduces the taxable base proportionally. For example, a single $200 taxable part with a 10% tax rate and a 20% discount: the discount drops the taxable base from $200 to $160, so tax is 0.10 × 160 = $16.00, not $20.00, and the total is (200 − 40) + 16 = $176.00.

Money is rounded to 2 decimals for display. The default tax rate is blank — enter your own; this tool never assumes a jurisdiction. This is a billing document, not a tax filing or an accounting record: verify sales-tax rates and rules for your area before sending.