How to Invoice for Expenses, Reimbursements & Mileage

To invoice a client for expenses, list each reimbursable cost as its own line item with a clear description and amount, reference or attach the receipts, and total those costs separately from your service fees. Bill expenses at cost unless your contract says you add a markup, and keep mileage and travel as distinct lines so the client can see exactly what they are paying for.

That is the short version. Below, we cover the difference between billable and reimbursable costs, how to decide whether to mark expenses up, the right way to list travel, mileage and per diem, and a worked example you can copy. This guide is specifically about passing on costs — if you want help setting hourly or day rates, that lives in our complete freelancer invoicing guide.

Billable vs Reimbursable Costs: Know the Difference

People use these two terms loosely, but they mean different things, and getting them straight stops awkward conversations at payment time.

• Reimbursable expenses are costs you paid out of your own pocket that the client agreed to repay you for — a flight you booked, materials you bought, a parking fee. You are not making money on them; you are getting your money back.
• Billable costs is the broader bucket of anything you charge the client for, which includes your time, your fees, and any expenses you pass on. A reimbursable expense is billable, but not everything billable is a reimbursement.

The practical takeaway: an expense is only reimbursable if the client agreed to it. The single biggest cause of expense disputes is a freelancer or contractor assuming a cost is "obviously" the client's responsibility when it was never written down. Agree the rules before you spend, not after.

A simple test: if you would have spent the money even without this client, it is probably your overhead. If you only spent it because of this engagement and they signed off on it, it is reimbursable.

What Usually Counts as a Reimbursable Expense

The exact list depends on your contract, but these are the costs clients most commonly agree to cover:

• Travel — flights, trains, taxis, rideshare, fuel, and parking incurred for the client's work.
• Mileage — driving your own vehicle, billed at an agreed per-mile or per-kilometre rate.
• Accommodation and per diem — hotels and a daily allowance for meals when an engagement keeps you away from home.
• Materials and supplies — physical goods, print costs, stock photography, or hardware bought specifically for the project.
• Software, licences and subscriptions — tools you bought solely to deliver this job, such as a one-off plugin licence or a paid font.
• Third-party fees — couriers, permits, or subcontractor invoices you paid on the client's behalf.

What Usually Does Not

Your general operating costs are baked into your rates, not billed separately. That normally includes your everyday office, your own computer, accounting software, internet, and the time you spend on admin. If you try to itemise these as "expenses," clients will push back — and they are usually right to.

Should You Mark Up Expenses?

This is the question that comes up most, and the honest answer is: it depends on what you agreed. There are three common approaches, and none of them is wrong as long as the client knows which one you are using.

1. Bill at cost (pass-through). You charge exactly what you paid, no more. This is the most common and the easiest to defend, because the receipt and the line item match to the penny. Most consultants and freelancers default to this.
2. Bill at cost plus a handling markup. Some businesses add a modest percentage — often somewhere in the region of 10–20%, though this varies widely — to cover the admin, cash-flow cost, and risk of fronting the money. This is legitimate, but it must be agreed in writing first.
3. Fold expenses into a higher rate. Instead of itemising, you quote a single all-in fee that already absorbs your expected costs. This keeps invoices simple but only works when you can predict the expenses accurately.

Whatever you choose, write it into the contract before the work starts. A line like "Pre-approved expenses are billed at cost" or "Expenses are billed at cost plus 15% handling" removes all ambiguity and protects the relationship.

If you do mark up, never disguise it. Showing a flight at its true price and then adding a separate, clearly labelled handling line is far more trustworthy than quietly inflating the flight figure. Clients forgive a transparent markup they agreed to; they do not forgive discovering a hidden one.

How to List Expenses on an Invoice

The golden rule is separation. Your professional fees and your reimbursable expenses should be visually and numerically distinct so the client can see at a glance what is your work and what is pass-through cost. Here is how to structure it.

Use One Line Item per Expense

Resist the urge to bundle everything into a single "expenses" line. Give each cost its own row with a specific description, the date, and the amount. "Return flight London–Berlin, 14 May" tells the client far more than "travel." Granular line items get approved faster because there is nothing to query.

Group Expenses Separately from Fees

Put your services at the top, then a clearly headed expenses section below. Many people show two subtotals — one for fees and one for reimbursable expenses — before the grand total. This makes your bookkeeping cleaner and helps the client code the costs correctly on their side.

Reference or Attach Receipts

Clients expect proof for reimbursements. You can attach a single PDF of all receipts to the email, or number each receipt and reference it on the matching line (for example, "see receipt 3"). Keep copies of every receipt yourself; tax authorities commonly expect you to retain records for several years, though the exact retention period varies by country.

Keep Descriptions Honest and Dated

Dates and specifics are what make an expense invoice auditable. If you want a refresher on the core fields every invoice needs — invoice number, dates, your details, the client's details — see our guide to what to include on an invoice. An expense invoice is a normal invoice with a well-organised costs section; it does not need a different format.

How to Invoice for Travel, Mileage & Per Diem

Travel is the most common reimbursable category and the one most likely to be queried, so it is worth handling carefully.

Travel Expenses

Flights, trains, taxis, and parking are usually billed at cost with the receipt attached. List each leg or each booking on its own line with the date and route. If the client has a travel policy — economy only, a hotel price cap, advance-booking rules — follow it, or get written approval before you book something outside it.

Mileage

When you drive your own vehicle, you do not bill fuel receipts — you bill mileage. Multiply the distance driven by an agreed per-mile or per-kilometre rate and show it as a single line item, noting the rate and the total distance. For example: "Mileage: 120 miles at the agreed rate." Many countries publish a standard or approved mileage rate that businesses commonly use as a reference point, but these change periodically and differ by country, so always confirm the exact figure with your client and check the current official rate rather than relying on a number you remember.

Per Diem and Accommodation

A per diem is a fixed daily allowance for meals and incidentals so you do not have to itemise every coffee. If you bill a per diem, state the daily amount and the number of days. Accommodation is normally billed at cost with the hotel invoice attached. Agree the daily allowance and any hotel cap upfront; per diem rates vary enormously by city and country.

A Worked Example

Imagine you are a consultant who spent two days on-site for a client. Your contract says expenses are billed at cost and you bill mileage at an agreed rate. Your invoice might look like this:

Professional fees

• Strategy consulting, 2 days on-site — 1,600.00
• Subtotal (fees): 1,600.00

Reimbursable expenses

• Return train ticket, 12 June (receipt 1) — 84.50
• Mileage, 60 miles at the agreed rate — 27.00
• Hotel, 1 night, 12 June (receipt 2) — 110.00
• Per diem, 2 days at the agreed daily rate — 50.00
• Subtotal (expenses): 271.50

You then add any applicable tax according to your own rules, show a grand total, and attach the two numbered receipts. Because fees and expenses are separated and every cost has a description and a date, there is nothing for the client to query — which is exactly how you get paid faster. You can build this layout in a couple of minutes with our free invoice generator, adding each expense as its own line item.

Do You Charge Tax on Reimbursed Expenses?

This is genuinely one of the trickiest areas, and the answer is firmly "it depends." Whether you add sales tax, VAT, or GST to a reimbursed expense hinges on your local tax rules, your registration status, and crucially whether the original cost already included tax.

• In some systems, a recharged expense is treated as part of your taxable supply, so you add tax on top of it the same way you do for your fees.
• In others, a genuine pass-through cost (sometimes called a disbursement) where you paid as the client's agent can be passed on without adding tax again.
• If the expense already had tax baked into the price you paid, charging tax a second time on the full amount can mean the client pays tax twice — which is exactly the trap careful invoicing avoids.

The rules differ significantly between, for example, the UK's VAT treatment of recharges and disbursements and the patchwork of US sales tax rules that vary state by state. Because the wrong call can leave you under- or over-charging tax, treat this as general guidance only and confirm your specific situation with a qualified accountant. To get a feel for the numbers and see how tax stacks on a subtotal, you can run figures through our VAT and tax calculator.

Best Practices for Billing Expenses

A few habits separate the people who get expenses reimbursed smoothly from those who end up arguing over a parking receipt:

1. Agree the rules in writing first. Define what is reimbursable, whether there is a markup, and any caps before you spend a penny.
2. Get pre-approval for anything large or unusual. A quick email confirming a big flight or a piece of equipment saves a painful conversation later.
3. Keep every receipt. Photograph receipts the moment you get them and store them with the project. You will need them for the client and, potentially, for tax records you may need to retain for several years.
4. Invoice expenses promptly. Bundle them with your regular invoice for the same period rather than letting them pile up; stale expenses are harder to verify and easier to dispute.
5. Separate fees from expenses every time. Two clear subtotals beat one mixed total for transparency and for your own bookkeeping.

If you are new to building invoices from scratch, our step-by-step walkthrough on how to create an invoice shows the whole process, and you can start from a blank invoice on the InvoiceGen homepage whenever you are ready.

Frequently Asked Questions

How do I invoice a client for expenses?

List each reimbursable cost as its own line item with a clear description and amount, attach or reference receipts, and total them separately from your fees. Keeping expenses in their own section, distinct from your professional fees, makes the invoice easy to approve and easy to reconcile on the client's side.

Should I mark up expenses I bill to clients?

Only if agreed in advance; many bill expenses at cost, while some add a small handling markup — set expectations in your contract. If you do add a markup, label it as a separate, transparent line rather than inflating the underlying cost.

How do I invoice for mileage?

Multiply miles or kilometres driven by an agreed per-mile rate and list it as a line item; reference the rate you agreed. Note the total distance on the line so the client can see how the figure was calculated, and confirm the current rate rather than relying on memory, as official rates change and vary by country.

Do I charge tax on reimbursed expenses?

It depends on your tax rules and whether the cost already included tax. This is general information, not tax advice — recharges, disbursements, and sales-tax treatment vary by country and even by state, so confirm your specific case with an accountant. You can model how tax sits on top of a subtotal using our VAT and tax calculator.