Expense reimbursement on invoices

Expenses on an invoice are costs you paid (or will pay) that the client agreed to cover: travel, stock, software seats, courier fees, venue hire. Treat them as pass-through lines, not as a quiet bump to your fee. When expenses and fees share one muddy total, tax, markup, and approval all get harder.

Agree before you spend

Reimbursable does not mean unlimited. Get a written yes on categories and a budget, even if it is a short email. Useful details:

• Which costs are in scope (flights, hotels, materials, subcontractors).
• A cap, or a rule like “pre-approve anything over $200.”
• Whether you may add a handling fee or must bill at cost.
• What proof they need (receipt PDF, booking confirmation, mileage log).

If the expense was not approved, do not surprise them on the invoice. Ask first, or absorb it.

How to show expenses on the PDF

Keep your fee lines and expense lines separate. Name each expense so a stranger can see what it was.

Notes can say: “Expense lines billed at cost as agreed 1 September. Receipts attached for rail and printing.” If you charge a markup, say the percent on the line or in the notes. Hidden markup is what clients remember.

At cost vs marked up

• At cost. Bill exactly what you paid. Simple, easy to audit, common for travel and materials.
• Marked up. Allowed when the contract says so. Show the base and the uplift, or show one line with “includes 10% handling” so nobody has to reverse-engineer it.
• Per diem or mileage. Use the rate you agreed, not a private number from a random blog. Log dates and distance if you bill mileage.

Tax on expenses (keep it honest)

Whether reimbursements are taxable, VAT-able, or outside the fee can change by country and by expense type. This guide will not pick your rate. Practical invoice habits that travel well:

• Do not blend expenses into a single “services” line.
• If some lines are taxable and some are not, label them or split the document. Discounts, tax, and totals covers the usual order of operations.
• Ask your accountant once for your common expense types, then reuse that pattern.

What to attach

Most clients want proof, not a story. Attach or link:

• Itemised receipts or invoices from the supplier.
• Booking confirmations for travel.
• A one-page expense summary that matches the invoice lines in order.

If the file is large, say in the email where the receipts live. An invoice that claims $400 of “misc travel” with nothing attached will sit in a queue.

Billing expenses on a later invoice

Sometimes the fee goes out first and expenses land later. That is fine. Use a new invoice number, reference the project and the earlier invoice, and list only the expenses (or the expenses plus any remaining fee). Do not quietly reopen the old PDF and edit the total. Numbering discipline still applies; see invoice numbering systems.

Notes on that follow-up can list the two receipts that make up $218.40 so AP does not have to open a second email thread. Keep the expense invoice number in sequence with your fee invoices; do not invent a parallel “EXP-” series unless the client’s portal requires it.

Currency and foreign receipts

If you paid in a different currency than the invoice, pick one clear conversion and document it. Clients reject mystery FX.

• Convert each receipt to the invoice currency with a stated rate and date (card statement rate, mid-market on the spend date, or the rate in your agreement).
• Put the foreign amount in the description: “Hotel, 2 nights, EUR 180.00 @ 1.08 = $194.40 (statement 12 Sep).”
• Bill the invoice currency you want reimbursed in. Do not leave AP to guess whether to wire euros or dollars.
• If the card later posts a different FX amount, either absorb the few cents or send a one-line correction before they pay. Silent gaps look like padding.

Mileage and per diem lines

Mileage and per diems are not receipt pass-throughs. They are agreed rates. Show the inputs so the line can be audited.

Attach a short mileage log (date, from/to, miles) when the amount is material. Do not invent a government rate if your contract named a different one. Speaking at a college? The honorarium invoice template keeps the honorarium and travel on separate lines.

What AP often asks for

• PO or job code in the PO / reference field, matching their purchase order.
• Receipts in the same order as the expense lines.
• A split between fee and reimbursables if their system posts them to different ledgers.
• Your tax ID where they require it on every vendor PDF, even for expense-only invoices.

If they need a cost centre on every line, put it in the description rather than hoping the email subject survives forwarding. Same idea as keeping payment references obvious in payment methods on invoices.

Common mistakes

• Padding the hourly rate instead of showing the expense.
• Rounding several receipts into one unexplained lump.
• Billing personal spend that was never client-related.
• Sending expenses months late, after the project PO is closed.
• Mixing deposit logic with expense logic. A deposit toward fees is a different document pattern (deposit invoices).

Checklist

• Expenses were pre-agreed or separately approved.
• Each expense line is specific and matches a receipt.
• Fee and reimbursement are visually separate.
• Markup, if any, is disclosed.
• Currency matches how you want to be reimbursed.
• FX or mileage math is written where a stranger can check it.
• PO or job code is on the PDF if the client uses one.

Put the lines together in the invoice generator or start from the small business template. Tiny Utility Lab runs FreeInvoicePDF as a free, ad-supported tool with no paywall.