Time and Materials Invoice: How to Bill T&M Work (With Example)

A time and materials (T&M) invoice bills the client for two things: the hours you actually worked, and the materials or expenses you actually spent — usually with a markup on the materials. You're billing real cost plus your labor, not a fixed price agreed in advance. It's the model contractors, consultants, and agencies fall back on when the scope is too fuzzy to quote a single number.

The catch is that T&M shifts risk onto the client. With a fixed price, you eat the overrun if the job runs long; with T&M, they do. That makes clients nervous, and a sloppy T&M invoice — vague hours, surprise material costs, an unexplained markup — is how that nervousness turns into a disputed bill. Done right, T&M is the most transparent way to bill: every dollar maps to an hour worked or a receipt paid.

This guide covers what belongs on a T&M invoice, how to structure labor and materials, how to handle expense markup honestly, and how to keep clients comfortable with caps and backup documentation. It builds on how to invoice for hours worked and sits alongside milestone billing and retainer invoices as one of the core project-billing models.

The short answer

A T&M invoice = labor (hours × rate) + materials/expenses + markup on materials + tax — each as its own clearly labeled section, backed by timesheets and receipts.

Labor: every task as hours × rate, broken out by person or rate if they differ.
Materials and expenses: itemized at cost, with receipts available.
Markup: a stated percentage on materials (commonly 10–20%), shown as its own line — never hidden inside inflated unit prices.
A cap or not-to-exceed clause so the client knows the ceiling before work starts.
Backup: a timesheet and receipts attached or available on request.

When T&M fits — and when fixed-price wins

T&M and fixed-price solve opposite problems. Pick by how well you can predict the job.

Bill T&M when:

The scope is unclear or evolving. Renovation behind a wall you haven't opened, a software integration against an undocumented API, a consulting engagement that will reshape itself after discovery. You can't quote what you can't see.
The client keeps changing direction. T&M makes scope creep cost them, not you. Every new request is just more billable hours and materials.
Materials cost is volatile. If lumber, parts, or third-party services swing in price, T&M passes the real cost through instead of forcing you to pad a fixed quote against the worst case.

Bill fixed-price when:

The deliverable is well-defined and you can scope it confidently.
The client needs budget certainty and won't accept an open meter.
You're fast — fixed-price rewards efficiency, T&M doesn't.

A common hybrid: fixed-price for the defined core, T&M for anything outside the agreed scope. For phased work with clear checkpoints, milestone billing is often a better fit than open T&M, because the client pays against accepted deliverables rather than a running meter.

Anatomy of a T&M invoice

A T&M invoice has the same header and footer as any project invoice — your details, the client's, an invoice number, dates, payment terms — but the body splits into clearly separated sections so the client can see exactly what they're paying for.

The three blocks, in order:

Labor — hours × rate, one line per task.
Materials and expenses — itemized at cost.
Markup — a percentage on materials, shown explicitly.

Then subtotal, tax, and total. Keeping labor and materials in separate blocks matters: clients scrutinize them differently. Labor they check against the timesheet; materials they check against receipts. Mixing the two into one column invites the "wait, what is this line?" question that stalls payment.

A worked example

Say you're a contractor who spent a week on a small build-out: 32 hours of labor at $85, $420 of materials, a 15% markup on those materials, and 8% sales tax on the lot. Here's the invoice body.

LABOR
  Description                          Hours   Rate     Amount
  Demolition + site prep                 8.0   $85    $680.00
  Framing + drywall                     14.5   $85  $1,232.50
  Electrical rough-in (rework)           6.0   $85    $510.00
  Final fit + punch list                 3.5   $85    $297.50
                                       -----        ---------
  Labor subtotal                        32.0        $2,720.00

MATERIALS & EXPENSES (at cost)
  Lumber + fasteners                                  $215.00
  Drywall sheets + compound                           $138.00
  Electrical box + conduit                             $67.00
                                                    ---------
  Materials subtotal                                  $420.00
  Markup on materials (15%)                            $63.00
                                                    ---------
  Materials total                                     $483.00

  Subtotal (labor + materials)                      $3,203.00
  Sales tax (8%)                                      $256.24
                                                    ---------
  TOTAL DUE                                         $3,459.24

A few things this layout does well:

Labor sums its hours. "32.0 hrs" is an easy number to accept; it ties straight to the attached timesheet.
Markup is its own line. The client sees $420 at cost and a separate $63 markup. There's nothing to discover later — markup hidden inside a $483 "materials" line is exactly the move that gets T&M invoices disputed.
Tax sits on the right base. Here it's applied to labor + materials + markup. Whether labor is taxable depends on your jurisdiction and the type of work — confirm before you assume, and see tax invoice for the field-level requirements.

Handling expense pass-through and markup honestly

Markup on materials is legitimate. You front the cash, you carry the procurement risk, you spend time sourcing — that's worth something. The 10–20% range is standard for contractors and agencies. The honesty problem isn't whether you mark up; it's whether the client can see it.

Two rules:

Bill materials at true cost, then add markup as a separate line. Don't inflate the unit price of the lumber and call it "materials." When the client eventually sees a receipt — and on T&M they're entitled to — a unit price that doesn't match torches your credibility on every other line.
Agree the markup percentage in the contract, before work starts. "Materials billed at cost plus 15%" in the SOW means the markup line on the invoice is something the client already signed off on, not a surprise.

Some expenses are better passed through at cost with no markup at all — things like permit fees, courier charges, or a software license bought specifically for the client. Marking up a $200 government permit reads as gouging. Reserve markup for materials you actually source and handle.

Not-to-exceed caps and how to set them

The single thing that makes clients comfortable with T&M is a not-to-exceed (NTE) cap — a ceiling on the total, agreed up front. "T&M, not to exceed $4,000 without written approval" gives the client the transparency of T&M and the budget safety of fixed-price.

How caps work in practice:

You bill actual time and materials up to the cap. If the job comes in at $3,200, that's what they pay — they don't owe the full $4,000.
Hitting the cap stops the meter. When you approach it, you stop and get written approval to continue before billing past it. Blowing through a cap without sign-off is how you end up eating the overage.
Set the cap with a buffer. Estimate the realistic cost, then set the NTE about 15–20% above it. Too tight and you're constantly asking for approvals; too loose and the cap stops reassuring anyone.

A related tool is the phased cap: a separate NTE per stage rather than one ceiling for the whole job. It keeps the client's exposure small at each step and gives natural re-approval points — close to how milestone billing works, but with the amounts still driven by actual hours.

Backup documentation — timesheets and receipts

On T&M, your documentation is the invoice's defense. The number on the page is only as trustworthy as the records behind it.

Timesheet. Date, task, hours, and a one-line description per entry — the same discipline as any hourly invoice. Attach it, or have it ready the moment a client questions the labor block. "32 hours" with no breakdown invites a fight; "32 hours, here's every entry" ends one.
Receipts. Keep every material and expense receipt. On T&M the client has a reasonable right to see them, and you may need to produce them at tax time anyway — see how long to keep invoices.
Approvals. Save the emails where the client approved extra work or signed off on going past a cap. That paper trail converts "this bill is too high" into "you approved this on the 14th."

Match the level of detail to the client. A long-standing client may accept summarized blocks; a corporate procurement team or a public-sector client will want the full timesheet and copies of every receipt with the invoice.

Billing cadence for T&M

Because T&M has no fixed total, the client's exposure grows every week until you invoice. Long gaps between invoices are where surprise bills come from. Bill on a tight, predictable rhythm:

Weekly or biweekly for active work. Frequent invoices keep each one small and the running total visible. The client is never shocked, because they've been watching the meter the whole time.
Monthly only for slow-burn or low-hour engagements, and even then pair it with reasonable payment terms so you're not floating a month of labor and fronted materials.
Always invoice promptly at period close, while the work and the receipts are fresh. A T&M invoice that lands three weeks late, full of line items the client has forgotten approving, is the hardest kind to get paid.

State the cadence in the contract alongside the rate, markup, and cap: "Billed biweekly, T&M not to exceed $8,000, Net 15."

Practical advice

Write the rate, markup %, NTE cap, and billing cadence into the contract before the first hour. Everything on the invoice should already be something the client agreed to.
Keep labor and materials in separate blocks, and show markup as its own line. Never bury markup in unit prices.
Bill materials at true cost and pass non-sourced expenses (permits, licenses) through with no markup.
Track hours as you go, not from memory on Friday — reconstructed timesheets underbill you and read as unreliable to the client.
Stop at the cap and get written approval before billing past it. A cap you quietly exceed is a cap that protects no one.
Invoice on a short, fixed cadence and summarize the running total in the email so the number is never a surprise.

FAQ

What's the difference between a time and materials invoice and an hourly invoice?

An hourly invoice bills labor only — hours × rate. A T&M invoice adds materials and expenses (usually with a markup) on top of that labor. If a job involves no pass-through costs, a plain hourly invoice is all you need. The moment you're fronting materials or expenses, it becomes T&M.

How much markup can I add on materials?

10–20% is the standard range for contractors and agencies, covering your procurement time, cash float, and risk. Agree the exact percentage in the contract and show it as a separate line on the invoice. Pure pass-through expenses like permits or licenses are usually billed at cost with no markup.

What is a not-to-exceed clause?

A not-to-exceed (NTE) cap is a ceiling on the T&M total, agreed before work starts: "T&M, not to exceed $4,000 without written approval." You bill actual hours and materials up to that ceiling and stop for re-approval if you'd go past it. It gives the client fixed-price budget safety while you still bill real cost.

Do I charge tax on labor in a T&M invoice?

It depends on your jurisdiction and the type of work — in some places services are taxable, in others only the materials are. Don't assume. Confirm the rule that applies to your work and apply tax to the correct base (labor, materials, or both). See tax invoice for the fields a compliant tax invoice needs.

How do I keep a client comfortable with an open T&M meter?

Three things: a not-to-exceed cap so they know the ceiling, a tight billing cadence (weekly or biweekly) so the running total is always visible, and full backup — timesheets and receipts — available on request. Transparency is what makes T&M work; the more the client can see, the less the open meter worries them.

Should I use T&M or milestone billing?

Use T&M when the scope is genuinely unpredictable and you can't define clean deliverables. Use milestone billing when the work divides into accepted phases you can price — it gives the client more certainty because they pay against deliverables, not an open meter. Many engagements start T&M during discovery, then switch to milestones once the scope firms up.

What backup do I need to attach to a T&M invoice?

At minimum, a timesheet (date, task, hours, description) for the labor block and receipts for the materials. Established clients may accept summarized blocks with backup on request; corporate and public-sector clients usually want the full detail attached. Keep approval emails too — they're your proof for any extra work or cap overage.