Hourly vs fixed-fee invoices
When to bill by the hour, when a fixed fee is cleaner, and how to write line items so the client can check the math without a follow-up call.
By Tiny Utility Lab, the team behind FreeInvoicePDF. Updated .
Hourly billing and fixed fees both belong on invoices. The invoice is not where you invent the model. It is where you show the model you already agreed, with line items a client can check in under a minute. Pick the wrong layout for the deal you struck and you invite a recalculation email.
When hourly fits
- Scope is fuzzy or likely to grow week by week.
- The client wants visibility into time spent.
- You are supporting, advising, or iterating rather than delivering one package.
- You have a rate card they already accepted.
Hourly invoices need enough detail that hours do not look made up. Group by week or by task, not one opaque line that says “consulting, 40 hours.”
When a fixed fee is cleaner
- The deliverable is clear (one site, one brand pack, one audit).
- You want to price the outcome, not the clock.
- The client hates reading timesheets.
- You can write a short scope so “done” is obvious.
Fixed-fee invoices still need a specific description. “Project fee” is weak. “Brand identity package as quoted 2 September 2026” is something finance can match to a PO.
Writing hourly lines
Show quantity (hours), rate, and amount. Add a date range in the description.
| Description | Qty | Rate | Amount |
|---|---|---|---|
| UX research interviews, 1-5 Sep | 6.0 | $120.00 | $720.00 |
| Prototype revisions, 8-12 Sep | 9.5 | $120.00 | $1,140.00 |
| Subtotal | $1,860.00 | ||
Round hours the way you agreed (nearest quarter hour is common). If you tracked 9.33 hours and bill 9.5, say so in your own notes so you can explain it once if asked. Attach or offer a timesheet summary when the client expects one; do not make them demand it after the due date. Lessons work the same way: a 90 minute session is 1.5 hours, as in the tutoring invoice template.
Writing fixed-fee lines
Usually one line for the package, quantity 1, rate equal to the fee. If the project had milestones, either invoice each milestone separately or list each stage as its own line with the portion of the fee. Retainer and milestone invoices walks through staged billing.
| Description | Qty | Rate | Amount |
|---|---|---|---|
| Landing page design and build (fixed fee) | 1 | $4,500.00 | $4,500.00 |
Mixing hourly and fixed on one invoice
Fine, if the agreement said so. Keep them as separate lines. Example: a fixed build fee plus hourly change requests after handoff. Do not fold extra hours into a silent bump of the fixed line. The client should see which dollars are package and which dollars are time.
| Description | Qty | Rate | Amount |
|---|---|---|---|
| Landing page design and build (fixed fee, quote 2 Sep) | 1 | $4,500.00 | $4,500.00 |
| Post-handoff change requests, 15-19 Sep (approved email 14 Sep) | 4.0 | $120.00 | $480.00 |
| Subtotal | $4,980.00 | ||
Same rule for expenses. Pass-through costs belong on their own lines, not stuffed into the hourly rate. Expense reimbursement on invoices covers that layout.
Change requests after a fixed fee
Fixed fee does not mean unlimited revisions forever. When the client asks for work outside the package, get a yes on hours or a small fixed add-on before you do it. Then invoice the overage as its own line or its own PDF.
Subject: Extra scope for landing page (estimate 4 hours @ $120)
Hi Sam, the homepage animation and extra form fields sit outside the fixed package we quoted 2 September. I can do them as time and materials at $120/hour, estimated at 4 hours ($480), not to exceed 5 hours without another note from you. Reply “approved” and I will schedule the work, then bill those hours on a separate line from the $4,500 fee.
When the work is done, mirror that approval language on the invoice so finance can match email to PDF. If they refuse the overage after you already shipped it, you are in dispute territory; see what to do when a client disputes an invoice.
Caps, estimates, and “not to exceed”
If you sold hourly work with a cap, show hours and rate as usual, and put the cap in the notes: “Not to exceed 20 hours ($2,400) without written approval.” If you hit the cap mid-month, stop or get approval before you invoice above it. An invoice that blows a cap without warning is how retainers die.
An estimate is not an invoice. If the number was only a range, settle the final figure before you bill. The difference between those documents is in estimate vs quote vs invoice.
Billing increments and minimums
Say the rounding rule once in the proposal, then use it on every hourly invoice.
- Nearest quarter hour is common (6.2 hours becomes 6.25). The babysitting invoice template bills 6:00 to 11:45 pm as 5.75 hours.
- Minimum booking (for example 1 hour) belongs in the notes when a short call still bills the minimum.
- Different rates for senior vs junior time need separate lines, not one blended rate that hides who did the work.
- Retainer of hours is still hourly math under the hood; the monthly fee line and any overage line should stay distinct. Retainer and milestone invoices covers the recurring pattern.
Which model to choose next time
- Choose fixed when you can define done, and you are faster than the client expects.
- Choose hourly when uncertainty is high, or when the client wants a dial they can turn down.
- Choose a hybrid when the core is fixed and overflow is hourly, and write that split into the proposal before work starts.
Field-by-field invoice basics still apply either way; see how to write an invoice. Line wording tips live in writing invoice line item descriptions.
Before you send
- Line style matches the commercial agreement.
- Hours or package description is specific enough to audit.
- Rate matches the quote, not last year’s rate card by accident.
- Approved overage is on its own line, not folded into the fixed fee.
- Total is obvious; no mystery math.
Draft it in the FreeInvoicePDF generator or jump in from the freelance or consultant template. Ads fund the tool; there are no payments on downloads.