Fixed Price vs Time & Materials — Which to Quote?

Every tradie faces this question on nearly every job: do you lock in a fixed price up front, or charge the customer for actual time and materials? Get it wrong and you either eat into your own margin or lose the customer's trust. The answer depends on the job — but the principles are simple once you know them.

Fixed price: when and why

A fixed-price quote means you give the customer one number and that is what they pay — regardless of how long it takes or how much material you use. In Australia, a written quote is generally treated as a fixed price under consumer law (unlike an estimate, which is a guess).

When fixed price works best

• Repeatable, predictable jobs. You have done fifty hot water installs or a hundred switchboard upgrades. You know exactly how long it takes and what it costs. The fixed price lets you bank the efficiency.
• Competitive residential work. Homeowners overwhelmingly prefer a fixed number — it removes uncertainty and makes comparing quotes easy. If you are competing for bread-and-butter residential jobs, fixed price is usually the way to go.
• Jobs you have inspected. Once you have seen the site and understand the scope, a fixed price is low risk for you and high confidence for the customer.

The upside

If you finish early or use less material, you keep the difference. On a job you have dialled in, a fixed price can earn you significantly more per hour than your standard rate. That is the reward for knowing your trade and being efficient.

The risk

If something goes wrong — hidden damage, asbestos, the customer changes their mind — you eat the cost. The classic "opened the wall and found…" scenario. You can protect yourself with a clear scope, explicit exclusions, and a variation clause, but the base risk is yours.

Time & materials: when and why

T&M means the customer pays for the actual hours you work (at your hourly rate) plus the actual materials you use (usually with a stated markup). You send an invoice at the end based on real numbers.

When T&M works best

• Unpredictable work. Old houses, renovations, fault-finding, storm damage — anything where you genuinely cannot know the full scope until you start.
• Open-ended or evolving scope. The customer says "while you are here, can you also…" and the job keeps growing. T&M means you get paid for the real work, not the guess.
• Maintenance and repair. A leaking pipe or a tripped circuit — you do not know if it is a $200 fix or a $2,000 fix until you open it up.
• Commercial or repeat clients. Businesses and property managers often prefer T&M for ongoing work because they understand the model and value the transparency.

The upside

You never lose money on surprises. If the job takes longer or costs more, the price adjusts. Your hourly rate and materials markup are guaranteed.

The risk

The customer may feel nervous about an open-ended bill. And if you are slow or inefficient, the bill goes up — which can create friction even if you are being completely honest. Transparency and communication are everything on T&M work.

The hybrid approach (often the smartest move)

You do not have to pick one or the other for the whole job. The best tradies often combine them:

• Fixed price for the known work — the stuff you can scope and measure.
• T&M for the uncertain part — the bit you will only see once you open the wall, pull up the floor, or start the diagnostic.
• A cap on the T&M component — "The exploratory work will be time and materials, but I will not go past $X without calling you first."

This gives the customer certainty on the bulk of the job and protects you on the unknown. It also makes you look professional and thoughtful — which is exactly the kind of tradie people hire and recommend.

How to protect yourself either way

• Written scope. Whether fixed or T&M, write down exactly what is included and what is not. "Excludes any asbestos removal, structural work, or council permits" saves you thousands one day.
• Variation clause. For fixed-price work: "Any work outside the agreed scope will be quoted separately before proceeding." Simple, fair, and it stops scope creep from eating your margin.
• Cap or estimate for T&M. Even if you are charging hourly, give the customer a "likely range" and a cap. "I expect this will be between $800 and $1,200. I will not go past $1,500 without discussing it with you first."
• Progress updates on T&M. Text the customer at the end of each day (or each visit) with a summary of hours and cost so far. No surprises on the final invoice.

How different trades typically price

There are no hard rules, but patterns emerge:

• Electricians — mostly fixed price for domestic (switchboard upgrades, power point installs, lighting). T&M for fault-finding and older properties.
• Plumbers — fixed for standard installs (hot water, tapware). T&M for blocked drains, leaks and renovation rough-ins where hidden issues are common.
• Builders/Carpenters — fixed for decks, pergolas, defined scope. T&M or cost-plus for renovations and anything involving existing structures.
• Painters — overwhelmingly fixed price (measure the surface area, cost the paint, quote it). T&M only for prep-heavy restoration work.
• HVAC — fixed for standard split-system installs. T&M for ducted work in older buildings or commercial fit-outs.