Plumbing taxes and sales tax, decoded (US and Canada): Plumbing Bench

The tax side that trips up plumbing owners: entity choice, deductible expenses, writing off the van and equipment (Section 179/CCA), quarterly/instalment taxes, and when to charge sales tax on materials vs. labor (US) or GST/HST/PST (Canada): the framework and the traps.

Nothing sinks a busy plumbing shop faster than a tax surprise: a sales-tax audit that says you should’ve been charging it on that repipe, or a self-employment tax bill you never set money aside for. The rules are genuinely different between the US and Canada, and even within the US they change at the state line. This is the framework and the traps. It is not a substitute for a CPA/accountant who knows your jurisdiction. Hire one; it’s the cheapest insurance you’ll buy. Tax figures, thresholds, and rates change every year, so treat every number here as a starting point to verify with the current IRS/CRA and state/provincial guidance, not gospel.

Entity choice: the decision under everything

How you’re structured drives how you’re taxed, what you can deduct, and how exposed your personal assets are if a job goes wrong.

Sole proprietor / partnership. Simplest and cheapest to run. Business income flows to your personal return. In the US you pay income tax and self-employment tax on the net; in Canada it’s your personal marginal rate. No liability shield, a real concern in plumbing, where a bad backflow or flood claim can be large.
LLC (US). Liability protection with pass-through taxation by default. Many established plumbing shops then elect S-corp treatment so a portion of profit comes out as distributions not subject to self-employment tax, but only above a certain profit level, and only if you pay yourself a reasonable salary first (the IRS scrutinizes this). Talk to a CPA about where the crossover is for your numbers.
Corporation (Canada). Incorporating can defer tax and access the small business deduction on active business income. It adds filing cost and complexity, so it usually makes sense once profit outgrows what you draw personally. A CPA runs the salary-vs-dividend math for your situation.

There’s no universally right answer: it’s a function of your profit, your risk, and your province/state. This is exactly the conversation to have with an accountant before year one closes, not after.

Deductible expenses: what plumbers routinely leave on the table

Track these relentlessly year-round: reconstructing them in March is how you overpay. Ordinary, necessary business costs for a plumbing operation generally include:

Vehicle: fuel, insurance, repairs, and either mileage or actual costs (see below). The service van is often the single biggest write-off.
Tools and equipment: from hand tools to drain cameras, jetters, and press tools. Big-ticket gear gets special treatment (next section).
Materials and shop supplies, CE and license renewals, trade/liability/workers’ comp insurance, bonding, phone and dispatch/field-service software, advertising, a home-office portion if you qualify, and professional fees (your CPA is deductible).

If you don’t know your true cost of doing business, you can’t price to beat it: our know-your-numbers KPI guide covers turning these costs into overhead and margin targets.

Writing off the van and the big equipment (US Section 179 vs. Canada CCA)

You generally can’t deduct a $60k van or a $20k jetter all at once as a plain expense: capital assets are recovered over time. But both countries have accelerators:

US: Section 179 and bonus depreciation. Section 179 lets you expense qualifying equipment and certain vehicles in the year you place them in service, up to an annual dollar cap that Congress adjusts. Heavy work vehicles and equipment often qualify; passenger-vehicle write-offs are capped. Bonus depreciation is a separate accelerator that was restored to 100% for most qualifying property acquired and placed in service after January 19, 2025, though the percentage has swung repeatedly with recent legislation. The limits, caps, and bonus percentage change frequently. Verify the current-year figures with the IRS (Publication 946) and your CPA before you rely on them.
Canada: Capital Cost Allowance (CCA). You deduct a percentage of an asset’s value per year based on its CCA class (vehicles, tools, and equipment fall into different classes with different rates). Recent years have offered enhanced/accelerated first-year write-offs on some assets. Confirm what’s in effect this year with the CRA, because these incentives are added and phased out over time.

Vehicle method (both countries): you generally choose between a per-kilometre/per-mile rate and actual expenses (fuel, insurance, repairs, depreciation) prorated by business use. Whichever you pick, you need a mileage log: undocumented vehicle claims are a classic audit loss. The IRS standard mileage rate and the CRA prescribed rate both change annually; look up the current one.

🇺🇸 US: the sales-tax question that has no national answer

Whether you charge sales tax (and on what) depends on your state, whether the work is residential vs. commercial, whether it’s a repair vs. a capital improvement, and how your contract is written (itemized vs. lump-sum). The general shape:

Materials (fixtures, pipe, water heaters, parts) are taxable somewhere in the chain: the open question is whether you pay it buying from the supply house, or you buy tax-free for resale and charge the customer. In several states the contractor is treated as the end consumer of materials: you pay sales tax at purchase and don’t charge the customer separately. In others you buy tax-free on a resale certificate and collect from the customer. Which applies is a state rule, not your choice.
Labor is a service, exempt in many states, but not all, and not always.
Residential vs. commercial matters. Some states tax construction/repair labor differently on residential versus nonresidential real property. Confirm your state’s treatment.
Capital improvements (a repipe or a new water-heater install can qualify) are often exempt to the customer (no tax on the invoice), though you still pay tax on the materials you bought. A straight repair is often treated differently from an improvement.
Contract type matters. More states give you reseller treatment (buy tax-free, charge the customer) on itemized contracts than on lump-sum ones.

If you regularly work across state lines, also check economic nexus: since the 2018 Wayfair decision, doing enough business in another state can obligate you to register and collect there.

What to do: don’t guess. Look up your state’s rule for plumbing/construction contractors on the state department of revenue site, decide your contract format deliberately with your CPA, and set up invoicing so you’re consistently right: sales-tax mistakes compound silently until the audit.

Income + self-employment tax (US). If you expect to owe $1,000+ for the year after withholding and credits, the IRS wants estimated quarterly payments: federal deadlines land around April 15, June 15, September 15, and January 15 (verify each year; they shift for weekends/holidays). Self-employment tax applies once net earnings hit $400+, and an Additional Medicare Tax of 0.9% layers on top of net earnings above $200,000 (single) or $250,000 (married filing jointly). Avoid penalties with the safe harbor: pay at least 90% of this year’s tax, or 100% of last year’s (110% if you’re a higher earner). Your state likely wants its own estimates too. Confirm current thresholds and the SE tax rate with the IRS.

🇨🇦 Canada: GST/HST, the $30k line, and input tax credits

The $30,000 threshold. Once your taxable revenue exceeds $30,000 in a single calendar quarter, or over the previous four consecutive quarters (whichever hits first), GST/HST registration is mandatory: you must charge, collect, and remit. Below that you’re a “small supplier” and can register voluntarily anyway, because…
Input Tax Credits (ITCs) are the payoff. Once registered, you recover the GST/HST you paid on your own purchases (van, tools, fixtures, materials) by claiming ITCs. That’s real money back, which is why many sub-$30k shops register voluntarily.
GST/HST applies to BOTH labour and materials. Unlike the US labor-often-exempt world, you charge GST/HST on the full invoice. The rate depends on the customer’s province: a 5% GST base out west, up to 13-15% HST in Ontario and Atlantic Canada. Confirm the current rate for the customer’s province with the CRA, as combined rates have changed.
PST/QST can layer on top. In BC, Saskatchewan, Manitoba, and Quebec a separate provincial sales tax may apply in addition to GST, with its own rules on what’s taxable for contractor work, including, in some provinces, tax the contractor pays on materials rather than collects. Check your province’s PST/QST treatment specifically.
Keep the paperwork. ITC claims must be backed by proper invoices showing the supplier’s GST/HST number. No paperwork, no credit, and the CRA checks.

Income tax (Canada): unincorporated, you report business income on your personal return; incorporated, the corporation files its own. Either way, set money aside: CRA also expects instalments once your net tax owing crosses the threshold. Verify the current instalment rules with the CRA.

Both countries: the money habits that keep you out of trouble

Separate the tax money. Every time you get paid, sweep the sales-tax/GST-HST portion and an income-tax reserve into a separate account. That money was never yours. Treat it that way and quarterly bills stop hurting.
Reconcile monthly, not at year-end. A shoebox of supply-house receipts in March is how you overpay and miss deductions. Use bookkeeping software (QuickBooks, Xero, Wave) and reconcile monthly.
Track deductible costs relentlessly: vehicle/mileage, tools, fuel, insurance, phone, software, home-office portion, CE/licensing.
Hire the CPA before you need them. A trades-savvy accountant saves more than they cost, on entity structure, sales-tax setup, and what’s deductible. It’s the single best tax move a shop owner makes.

If financing big-ticket work like repipes and water heaters is part of your sales motion, note that how you present and price those jobs interacts with tax: our consumer-financing guide covers the fee side.

Checklist

The bottom line

In the US, sales tax is a state-by-state, contract-by-contract puzzle and you self-manage quarterly income/SE tax; in Canada, you charge GST/HST on everything past $30k and claw back your own tax via ITCs. Your entity choice sets the frame, and the van and equipment are your biggest levers via Section 179 or CCA. In both countries, the shops that don’t get hurt do three boring things: separate the tax money the day it lands, keep clean monthly books, and pay a good accountant. Do those and tax season is a formality, not a crisis.

General information for plumbing business owners, not tax or legal advice. Tax rules, rates, and thresholds vary by state/province and change every year: verify the current figures with the IRS/CRA and your state/provincial revenue authority, and confirm your situation with a qualified accountant.

This guide is general information for independent plumbing contractors, not legal or financial advice. Some outbound links may be affiliate or sponsored links, which are disclosed and never affect our recommendations.

Plumbing taxes and sales tax, decoded (US and Canada)