Invoice Worked Example: Line Items, Tax and Deposit Math

This invoice worked example shows how line items become a subtotal, how illustrative tax is calculated, and how a deposit reduces the final balance due.

This worked invoice starts with four job-based line items, calculates an illustrative 7% tax amount, records a $300 deposit, and shows the remaining balance. If you need the general visual anatomy first, read what an invoice looks like; this page focuses on checking the numbers.

The example below is an electrical panel upgrade. Other trades can use a similar itemized layout, with their own charges, payment schedule and applicable tax treatment.

The invoice, filled in

Here's illustrative INV-2107, issued September 22, 2026, for a 200-amp panel upgrade with a 15-day payment window. The sample uses 7% of the full subtotal to demonstrate the arithmetic; it is not an Indiana contractor tax calculation. Indiana's tax treatment depends on the contract and taxable materials, as explained in DOR Bulletin 60. Confirm the taxable base, rate and invoice requirements for the actual job before using this layout:

Where each number comes from

Every figure on that invoice traces back to a specific calculation, and a reader (or an accounts-payable clerk) should be able to check each one:

• Subtotal ($1,337.50). The dispatch fee, labor, materials, and permit added together: $95.00 + $517.50 + $640.00 + $85.00.
• Sales tax ($93.63). For this arithmetic example only, 7% of the $1,337.50 subtotal rounds to $93.63. The taxable base for a real job depends on its location, contract and applicable rules; do not copy this assumption as tax guidance.
• Total ($1,431.13). Subtotal plus tax.
• Deposit ($300.00). An advance payment collected before the job started, recorded as a payment against this invoice rather than folded into the line items above.
• Balance due ($1,131.13). Total minus the deposit already received. This is the number the client actually needs to pay.

Showing the deposit as a separate line, rather than quietly reducing the materials price, keeps the math auditable. Anyone looking at this invoice a year from now can see the full job value, what was paid up front, and what settled the balance.

The fields every invoice needs

Strip the formatting away and this invoice, like any other, is built from the same core set of fields:

1. Business and client details. Who is billing whom, with enough contact information to follow up.
2. A unique invoice number. INV-2107 identifies this specific bill and nothing else. Our invoice number generator guide walks through keeping that sequence clean across a full month of jobs.
3. Issue date and due date. A calendar date, not just a term like "Net 15," so there's no ambiguity about when payment is late.
4. Itemized charges. One row per cost type, described specifically enough that the client can match it to the work done.
5. Subtotal, tax, and total. The math shown, not just the final number.
6. Payments already received. Any deposit or partial payment, netted against the total to show the real balance due.

Why the numbers need to be exact

Itemized charges let the client check how the total was calculated; they do not guarantee faster payment. According to QuickBooks' 2026 Small Business Late Payments Report, 59% of small businesses were carrying invoices more than 30 days overdue in 2026, up from 47% the year before, and businesses with unpaid invoices are owed $17.7K on average. A client who has to guess at how a total was calculated has an easy excuse to sit on payment. A client who can check every row against their own memory of the job doesn't.

That's also why the due date belongs on the invoice itself, not just in a follow-up email. If Dana's balance is still open after October 7, both sides can point to the same document and agree it's overdue.

Different trades, different line items

The layout above holds regardless of trade, but what fills the rows changes. Electrical invoice software needs to handle labor, marked-up materials, and permit fees on the same job, the way INV-2107 does above. HVAC invoice software has to account for a diagnostic fee plus parts and labor that can vary wildly between a $150 repair and an $8,000 system replacement. Photography invoicing software works differently again: a session fee, a package price, and often a separate deposit collected weeks before delivery, rather than materials at all.

The seven fields don't change. What you're allowed to leave off, and what needs its own line, does.

Build this invoice yourself

WaffleInvoice's free invoice maker lays out every field from the example above (business details, client details, line items, tax, and payments received) and totals the math for you as you type, so a typo in one row doesn't throw off the balance due. If you're comparing tools rather than templates, WaffleInvoice's feature overview and the industry-specific invoicing pages cover how the line items above adapt for HVAC, photography, and other service trades. If you still want the plain-template version of this same layout, our free invoice template for Word guide covers what's in it and where a static template runs out of road.