The invoice does a job the work itself cannot. The customer was not under the sink with you. They cannot judge whether the repair took the right amount of time or whether the part you installed was the right one. What they can judge is the piece of paper at the end. A plumbing invoice that reads like a clear record of what was done gets paid. One that reads like a demand for a round number gets questioned, and a questioned invoice is a slow invoice.
What to put on a plumbing invoice: the must-have lines
Start with the header. The invoice needs your legal business name, your contractor or plumbing license number where your state requires it, your phone number, and your remittance address. Then the customer's name, the service address where the work happened, and the billing address if it differs. For a property manager or a landlord paying for a tenant's unit, the service address and the billing address are not the same, and an invoice that blends them is the one that sits in an approval queue for a month.
Give every invoice a unique number and a date of service. The number is how both of you reference the job later. The date matters more than it looks: in most of the construction trades, payment timing and any lien or prompt-payment rights run from a date tied to the work or the invoice, and those windows are short. Below the header come the lines that describe the job, and the order of those lines is the rest of this guide. At a minimum you want a service call line, a labor line, itemized parts, any disposal or trip fee, the sales tax that applies in your state, the total, your payment terms, and your warranty. Each of those answers a question the customer would otherwise ask by text.
Separate labor from parts, because it can change the tax
The most common plumbing-invoice mistake is one line that reads "Replace water heater: $1,450." It feels clean. It is the most expensive line you can write, for two reasons. The first is that a single number invites the customer to relitigate the whole job, because there is nothing on the page to anchor the price to. The second is tax, and it is the part most plumbers do not price in.
Whether you charge sales tax on labor, on materials, or on the whole ticket depends on your state and on whether the work counts as a repair to tangible property or an improvement to real property. Several states tax the two differently, and the way you write the invoice decides which rule applies. Minnesota is the clearest example. There, repair labor is not taxable as long as the labor charge is stated separately from parts on the customer's bill. Combine the labor and the materials into one charge and the entire amount becomes taxable.4 A plumber who lumps a $300 labor charge into a single line with $200 of parts can turn a tax-free $300 into $500 of taxable base, and the customer pays the difference on a line they never needed to.
Other states run the rule the other way. New York treats charges for materials and labor billed for a repair or maintenance job, including markups, as taxable when the work is on real property.5 The point is not that one state is right. The point is that the labor-versus-parts split is not cosmetic. It is a number on the invoice that the tax rules read directly, so you separate the two and you learn how your own state treats each. The mechanics of which line gets taxed are covered more fully in the guide to invoicing for small HVAC shops, and most of it applies to a plumbing shop without change.
The service call and diagnostic line
Put the service call on the invoice as its own named line, even when you waive it. This is what you charge to show up and diagnose before any repair begins. In 2026 a residential plumbing service call commonly runs $50 to $200, and it usually covers the trip and the first part of the visit.1 A customer who sees "Service call and diagnostic: $99" and then sees it credited against the repair reads it as a discount you gave them. A customer who never sees it assumes the visit was free and pushes harder on every other line. The fee is doing work whether or not you collect it, so show it.
How much that line should be, and whether you should fold it into the first hour or keep it standalone, is its own decision. We worked through it in the guide on how to set a plumbing service call fee. Whatever number you land on, it belongs on the invoice as a line, not buried in a labor total.
Itemize parts at the price the customer pays
List the real parts: the water heater, the fixture, the supply lines, the valve, the wax ring. Charge them at the price the customer pays, with your markup already in the number, not at your cost from the supply house. Markup is not padding. It pays for the run to the supplier and the cash you fronted on the parts before the customer paid a dollar, and it funds the warranty you now carry because you supplied the part rather than the homeowner buying it off a shelf. Across the trades, materials markup commonly runs from roughly 20 percent on standard stock to higher on specialty or low-volume items.2
For an expensive item like a water heater or a pump, put the manufacturer and model number on the line. It documents exactly what the customer received, it makes a future warranty claim simple, and it removes the "is this the cheap one?" question before it gets asked. Small consumables, the tape, the solder, a handful of fittings, are not worth a line each. Roll them into one "materials and supplies" line so the invoice stays readable. The goal is an invoice a customer can scan and understand in fifteen seconds, not a parts manifest.
Where the license number and warranty terms belong
In many states the license number is not optional on the invoice. California is the strict example: the Contractors State License Board requires the license number on contracts, on invoices, and on advertising, and a home improvement contract over $500 has to be in writing and carry the license number along with the scope, the total, and the payment schedule.3 Even where your state is quieter about it, the license number on the invoice is a trust signal that costs you nothing and tells the customer they hired a licensed plumber, not a handyman working out of a truck.
The warranty line is where most disputes get settled, because it sets the expectation in writing before there is anything to argue about. A short line such as "90-day warranty on labor, manufacturer warranty on parts" tells the customer what they are covered for and, just as usefully, what they are not. When a call comes in four months later about a part failure, the invoice already answered it. Without that line, every later failure becomes a negotiation about what you implied at the door.
A worked plumbing invoice: water heater replacement
Here is the same water heater job written the way this guide argues for. The numbers are an illustrative example, not a quote. The labor rate sits inside the common 2026 residential band of roughly $75 to $150 an hour for standard work,1 and the sales tax shown is a placeholder rate applied only to the materials, the way a separately stated labor state would handle it.4 Disposal is shown here as a non-taxable service fee, the same way labor is treated; states vary on this, so check how your own department of revenue treats it.
| Line | Detail | Amount |
|---|---|---|
| Service call and diagnostic | Trip and assessment, credited to this repair | $0.00 |
| Labor | Remove and haul old 40-gallon gas water heater, install new unit, reconnect gas, water, and venting, test. 3.5 hrs @ $110/hr | $385.00 |
| Water heater unit | 40-gallon gas, atmospheric vent (mfr / model on file) | $680.00 |
| Thermal expansion tank | Code-required where applicable | $65.00 |
| Connectors, gas flex, fittings | Supply lines, gas connector, drain pan | $95.00 |
| Materials and supplies | Solder, tape, sealant, small consumables | $25.00 |
| Disposal | Haul-away and recycling of old unit | $40.00 |
| Sales tax | Applied to materials only (example rate 7%) | $60.55 |
| Total due | Net 15. Payable by card, check, or transfer. | $1,350.55 |
Same job, same total ballpark as the one-line version, but every number on the page answers a question. The customer can see the unit was a 40-gallon gas heater, that the labor was three and a half hours of named work, that the tax fell only on the parts, and that the old unit haul-away was a real cost and not a hidden one. There is very little left to dispute. Add the warranty line and the license number at the foot, and the invoice is doing the collection work for you.
Payment terms that get you paid
State the terms on the invoice, in plain words, with a due date and not just a label. "Net 15" means little to a homeowner; "Payment due by June 24" is unambiguous. For a one-time residential repair, due on receipt or due within a few days is normal and protects your cash. Reserve longer net terms for the commercial and property-manager accounts that require them, where a 30-day cycle is the cost of doing the work at all. The single biggest lever is not the length of the term. It is whether the term is written down at all, because a customer cannot be late for a deadline that was never set.
Then follow up on what goes unpaid on a schedule, rather than whenever it crosses your mind. Chaser's 2022 Late Payments Report found that businesses chasing 90 percent or more of their invoices are the most likely to be paid within a week of the due date, and that pairing SMS reminders with email raised the odds of payment within a week by 56 percent over email alone.6 You cannot follow up on an invoice you never sent, which is the real reason to get the invoice out the same day the job is done. For the cadence of when each reminder should go out, see the guide on when to send invoice reminders.
One point sits upstream of the invoice. The cleanest invoice is the one that confirms a number the customer already agreed to. If you quote the job first, the invoice is just the receipt, and the payment conversation is mostly over before it starts. Whether to charge for that quote in the first place is its own call, worked through in the guide on whether plumbers should charge for estimates. The same line discipline shown here carries straight across to the other trades; the guide to what to put on an electrical invoice walks the same structure with the code reference added.
Put the labor, the parts, and the tax on one clean invoice
We built EosLog's invoice generator so the lines this guide argues for are already there: a named service call, a separate labor line, itemized parts with markup, a materials-and-supplies catch-all, and a tax line that sits on the parts. Fill it out, and the PDF that comes out the other side is one a homeowner or a property manager can read and pay without picking up the phone.
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Sources and further reading
- HomeGuide, "Plumber Cost Per Hour (2026)" (residential plumbing rates commonly $75 to $150 per hour for standard work; service call fees $50 to $200; emergency and after-hours $150 to $300 per hour).
- Angi, "Average General Contractor Markup" (typical materials and trade markup ranges; markup covers procurement, carrying cost, and warranty on supplied parts).
- California Contractors State License Board, "Advertising Guidelines for Contractors" (license number required on contracts, invoices, and advertising; home improvement contracts over $500 must be in writing and include the license number, scope, total, and payment schedule).
- Minnesota Department of Revenue, Sales Tax Fact Sheet 152, Labor — Installation, Fabrication, Construction, and Repair (repair labor is not taxable when the labor charge is separately stated from parts on the customer's bill; combining labor and parts into one charge makes the entire amount taxable).
- New York State Department of Taxation and Finance, "Contractors — Repair, Maintenance, and Installation Services to Real Property" (charges for materials and labor, including markups, billed for repair or maintenance to real property are taxable).
- Chaser, "The 2022 Late Payments Report" (invoice follow-up rate and the effect of pairing SMS reminders with email on payment within a week).
This guide reflects general US small-business plumbing practice as of 2026 and is not legal, tax, or licensing advice. Sales-tax treatment of labor and materials, contractor and plumbing license display rules, home improvement contract requirements, lien and prompt-payment deadlines, and warranty obligations vary by state and locality and change. Verify any rate, tax treatment, license-display requirement, and warranty term with your state department of revenue, your state licensing board, and your accountant before relying on this article for a live invoice.