How to invoice as a consultant

Consulting is sold differently from production work — clients are buying judgement, not deliverables you can count — so the invoice has to make a less tangible service look concrete and easy to approve. Here’s how consultants bill, and how to get paid for the work that’s easiest to give away.

How consultants actually bill

Most consulting engagements price one of four ways:

• Day rate — the default for project and on-site work. You quote, say, $1,200/day and invoice the days delivered. A clean unit clients understand.
• Half-day rate — useful for workshops, reviews or a single session. Price it at more than half a day rate (often 60%), because the setup and context-switching cost is the same.
• Monthly retainer — a fixed monthly fee for ongoing advisory access, usually capped at a number of days or hours. Predictable income for you, predictable budget for them.
• Fixed project fee — a single price for a defined deliverable (a strategy, an audit, an implementation plan). It rewards your efficiency and is the easiest thing for a client to sign off.

Whichever you use, set it deliberately rather than by gut — the freelance rate calculator and the guide on how to set your freelance rate apply just as much to a consulting day rate.

Bill for advisory time — the part you under-bill

The single biggest leak in consulting is advisory time: the “quick call”, the email review, the Slack question, the read-through of someone else’s draft. It feels rude to bill for, so consultants give it away — and then resent the client who consumes the most of it.

Fix it at the agreement stage, not the invoice stage. Either fold advisory access into a retainer with a clear cap, or state a minimum billing increment (e.g. calls billed in 30-minute units). Then track it as it happens — a call you log the same day gets invoiced; one you try to remember at month-end gets forgotten. Itemise it honestly on the invoice (“Advisory call, 14 May, 0.5 day”) so the client sees what they’re getting.

What goes on a consulting invoice

A consulting invoice carries the usual essentials — a sequential number, your and the client’s details, issue and due dates, total and any tax, and how to pay — plus a few consultant-specific lines:

• Days or sessions delivered, with dates, so the client can reconcile against their own diary;
• The engagement or PO reference, especially with larger clients;
• Expenses and travel, kept separate from fees;
• A short scope note for fixed-fee work, restating the deliverable.

Build one in a couple of minutes with the invoice generator.

Expenses, travel and disbursements

Agree the expense rules before you start. Travel, accommodation and subsistence are normally billed at cost with receipts attached; some consultants add a modest handling markup, which is fine if it’s disclosed up front. Disbursements — costs you pay on the client’s behalf, like a software licence or a venue — should be passed through at cost and listed separately from your fees, so there’s no suggestion you’re marking up someone else’s invoice. List every expense as its own line; a lump “expenses: $900” invites a query.

Retainers and deposits

For ongoing advisory, a retainer agreement is worth setting up properly — fixed monthly fee, a usage cap, and what happens to unused or overrun time. For larger one-off engagements, take a deposit (commonly 25–50%) before work begins; it filters out clients who were never going to pay and funds the early effort that’s hardest to recover if things stall.

Statements for regular clients

A client you bill every month soon has a stack of invoices, and “which ones are still open?” becomes a recurring friction. Send a monthly or quarterly statement summarising what’s been invoiced, paid and outstanding. It saves both sides reconciling and quietly surfaces anything that’s slipped overdue.

Set your terms, bill the advisory time, and most invoices pay on schedule. For the few that drift past the due date, Duefy chases them automatically so you don’t have to.