The question gets asked from both sides of the invoice: a plumber deciding whether the drive to the supply house belongs on the bill, and a homeowner holding a bill with a second trip on it. The rule is the same from either chair, so this guide writes it for the plumber and gives the customer's side its own section near the end.
The scope is a parts run or a second visit on a repair the shop is already doing. The first-visit fee is covered in how to set a plumbing service call fee, and a return trip caused by a fixture the customer bought is covered in should plumbers install customer-supplied fixtures.
The rule: whose job was it to have the part?
A missing part falls into one of three buckets, and the bucket decides who pays for the trip back.
| Bucket | What it means | Whose cost | Where it lands |
|---|---|---|---|
| Truck stock | A part this shop installs often enough that it should already be on the truck | The shop's | Nowhere on the invoice. The trip is overhead. |
| Supply-house run | A part the shop does not carry, on the shelf at a counter the same day | The job's | One trip charge, or built into the parts price. Never both. |
| Special order | A part that has to be ordered and arrives days later | The job's | A second visit, priced on the quote and approved first. |
The sorting question fits in one sentence: should this shop have had this part in the truck? If yes, the trip is yours. If no, the trip is a cost the job created, and the rest of this guide is about collecting it without an argument.
One condition applies to both of the job's buckets: the customer hears the charge, and agrees to it, before the truck leaves. A trip charge the customer approved is a line item. One the customer first sees on the final invoice is a dispute.
Truck stock: the trip back is your overhead
A trip for a part the shop installs every week is the cost of a stocking decision the shop made earlier. The customer did not choose what goes in the truck, so the gap belongs to the shop.
Pull the last quarter's invoices and sort the parts by how often they appear. The top of that list is truck stock by definition, because the shop has already shown it sells them, and any part on it that is not in the truck bin is a standing invitation to a return trip.
The arithmetic favors stocking. In the worked example below (illustrative numbers), one missed trip costs the shop about $111 in fuel and billable time, which is more than the $45 cartridge in that example sells for. A part that costs less than one trip pays for itself the first time it prevents a miss.
On an hourly job, stop the clock when the truck leaves the property for a truck-stock miss. Billing drive time to fetch a part the shop should have carried passes the shop's stocking gap to the customer, and it reads as padding. On a flat-rate job nothing changes: the price already assumed the part would be on the truck.
Supply-house runs: pay for the trip once, not twice
Do plumbers charge for going to get parts? Some do, and the version that holds up charges in exactly one place. A supply-house run is the middle case: the part is not on the truck, and a counter across town has it on the shelf. The trip is a cost the job created, so the shop can recover it. The mistake is recovering it twice.
A run can be paid for in three places. The first is the markup on the part. Markup is meant to cover costs like this one, and the materials markup guide breaks down how the supplier trip and the cash tied up in the part cost the shop money without showing up on any receipt. The second is a visible trip charge, a flat line on the quote. The third is the labor clock, with drive time to the supply house billed at the shop rate on an hourly job.
Pick one for the shop and use it every time. If the markup is meant to cover the run, the run is already paid, and a trip line stacked on top bills the customer twice for one drive. If the shop breaks the run out as its own line, the markup on that part should not also be counting on the same drive.
A flat trip line is the easiest of the three to get approved, because the number is fixed before the technician leaves. The labor-clock version works only when the customer was told in advance that drive time to the supplier is billed, since nobody knows the final number when they agree to it.
Special-order parts and the second visit
A special-order part is the clearest case for a billable second trip. The part was never going to be in the truck, and the second trip exists because the customer chose to wait for the right part.
Structure it as one job done in two visits, not two jobs. The first visit diagnoses the problem and makes the fixture safe. If the shop charges a first-visit fee, credit it against the repair when the repair is done; the service call fee guide covers how that credit works. The second visit is the repair visit, priced as the repair. A second service-call fee for finishing the repair the first fee diagnosed reads as double billing to the customer. Any added charge for the second dispatch belongs on the quote as a return-visit line, approved before the first visit ends.
The part itself is cash the shop fronts for one customer's job, and a special-order part may not be returnable. Treat it as a deposit question and collect the part cost when the order is placed. The deposit guide covers putting it on the quote.
Say it before you leave: the sentence that makes the trip billable
The whole policy depends on a thirty-second conversation at the door. Here is wording that works for a supply-house run:
"That cartridge is not on my truck. The supply house has it, and the run is $65. I will be back in about an hour. I am sending the revised quote to your phone now, and I will leave as soon as you approve it."
The $65 is an example, not a market rate. The wording states the price and the time, and it ends on an approval instead of an assumption, so there is nothing left to discover on the final invoice.
Say it out loud, then send it. The sentence is a conversation, and the revised quote on the customer's phone is the record. A return trip is a change to the original quote, so it is handled like any other change: the new line is written down and approved before the work it describes. The extra work guide covers the mechanics.
State guidance already says the same thing about changes to a job. California's Contractors State License Board tells consumers that a written contract is required for home improvement projects over $500, and that when the price or scope of work changes, the change "MUST be done with a written 'Change Order,' signed by the customer and contractor prior to the change."1 Illinois's attorney general says a written contract "with all costs enumerated is required for home repair or remodeling work over $1,000," that the contract must state "total cost, including parts and materials and any charge for the estimate," and that a homeowner should confirm the contract includes "a description of how change orders will be handled."2
Whether a given service call falls under rules like those depends on the state and the job, and a $200 repair is below both thresholds. The habit the rules encode applies anyway. The change is agreed before it happens, and it is written down.
Worked example: one shower valve, three invoices
Example, with illustrative numbers. A shower valve will not shut off. The quote on site is $240: $195 for labor and $45 for the cartridge. The technician pulls the valve trim, identifies the cartridge, and finds it is not on the truck. The supply house is ten miles away.
The run has a cost whether or not anyone bills it. The IRS standard business mileage rate, its figure for the deductible cost of operating a vehicle for business, is 76 cents a mile for the second half of 2026, so twenty miles round trip is $15.20.3 The run takes 50 minutes with the time at the counter, and the shop's loaded rate in this example is $115 an hour, a round number chosen for the example. For scale, the Bureau of Labor Statistics put the median wage for plumbers, pipefitters, and steamfitters at $30.67 an hour in May 2025, and that is wages alone, before the truck and the insurance are counted.4 Fifty minutes at $115 is $95.83 of billable time, so the run costs the shop about $111.
The same run can be invoiced three ways.
| Way | What the customer saw before the truck left | Final invoice | What the shop recovers of the $111 |
|---|---|---|---|
| 1. Absorbed | Nothing. No charge expected. | $240 | $0. The right outcome for a truck-stock miss, and a gift on a part the shop could not have carried. |
| 2. Priced before leaving | A revised quote with a $65 parts run line, approved on their phone. | $305 | $65. The customer agreed to the line, so it is paid. |
| 3. Added at the end | Nothing. | $305, with a $65 line the customer sees for the first time | Whatever the customer decides to pay. The line was never agreed to, so it is open to dispute. |
Ways 2 and 3 carry the same $65 line and the same $305 total. The only difference is when the customer saw it. Way 2 recovers $65 of the $111, and the $46 gap is the shop's call: it priced the line at what a customer would approve on a $240 repair. A shop that wants the full $111 back can price the line at $111, and will have a harder time getting it approved.
If the cartridge had been a stock part, way 1 is the only fair outcome, and the $111 is the price of not keeping a $45 part in the bin.
The customer's side of the same rule
When a customer pushes back on a trip charge, the first check is whether they heard about it before the work. If the revised quote is on file with their approval, the conversation is short: here is the line you approved, and here is when you approved it. If it is not on file, the cheaper move is to remove the line and fix the process so the next one is approved first.
If you are the customer holding a bill with two trips on it, the same rule gives you two questions. Was this a part the plumber should have had on the truck? And was the trip charge on a quote or message you approved before the plumber left? A plumber who can show an approved quote has a charge you agreed to. A plumber who cannot has a line you are entitled to question. If the conversation goes nowhere, your state's contractor licensing board or attorney general's consumer office is the place to ask what your state requires.
When to eat the trip anyway
Some trips should not be billed even when the policy allows it. A trip caused by the shop's own mistake, such as a wrong part ordered or a misdiagnosis on the first visit, is the shop's cost in every case. A trip charge that would be a large share of a small repair is another: a $65 line on a $90 job reads as a penalty, and absorbing it or building it into the next quote costs less than the argument.
When you do absorb a trip, put it on the invoice anyway as a line that reads "Parts run, no charge." The customer sees what the trip cost you, and the shop has a record of how often it happens. Several of those lines in a quarter is the stocking list from the truck-stock section writing itself.
Put the return trip on the quote before the truck leaves
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Sources and further reading
- California Contractors State License Board, What Is a Contract? (written contract required for home improvement projects over $500; written change order signed before any change in price or scope).
- Illinois Attorney General, Home Repair and Construction: What You Should Know (written contract with all costs enumerated required over $1,000; consumer checklist includes how change orders will be handled).
- Internal Revenue Service, Standard mileage rates (business rate of 76 cents per mile, July 1 through December 31, 2026).
- U.S. Bureau of Labor Statistics, Occupational Outlook Handbook, Plumbers, Pipefitters, and Steamfitters (median wage $30.67 per hour, May 2025).
This article is general information, not legal advice. Written-contract and change-order requirements for plumbing work vary by state and by job size, and many service calls fall below the dollar thresholds that trigger them. Confirm what applies with your state licensing board or a local attorney before relying on this article for a specific job.