How to Invoice for Hourly Work
Billing by the hour sounds simple — hours times rate — until you're turning a week of notes into an invoice and deciding what 1 hour 40 minutes is worth. Hourly invoices get paid fastest when the client can see how the hours were spent and the rules for counting them were agreed up front.
This guide covers tracking time, choosing a billing increment, converting minutes to decimal hours, handling travel and different rates, and writing hourly line items that answer the client's questions before they ask them.
Track time as you work
Reconstructing hours from memory at month end usually undercounts. Log start and stop times, or use a time tracker, and note the client and the task as you go.
Keep the log even if the client never asks for it. It's your evidence if an invoice is questioned, and it shows which tasks consistently take longer than you quote.
Agree a billing increment and rounding rule
Few people bill to the exact minute. Common increments are 6 minutes (a tenth of an hour, widely used by lawyers), 15 minutes, and 30 minutes, and many trades charge a minimum of an hour for any call-out.
Put the rule in your contract or engagement letter — for example, "time is billed in 15-minute increments, rounded up per task" — and apply it consistently. Rounding every small task up adds up fast, and a client who sees a dozen 0.25-hour entries for two-minute emails will notice, so group quick emails and calls into one entry per day.
Convert minutes to decimal hours
Invoices use decimal hours, so 1 hour 30 minutes is 1.5, not 1.30. Divide the minutes by 60: 15 minutes is 0.25, 20 minutes is 0.33, 40 minutes is 0.67, and 45 minutes is 0.75.
The mistake to avoid is writing 1.40 for 1 hour 40 minutes. At $90 an hour, 1.40 bills $126, when 1 hour 40 minutes is actually worth $150. Thirds of an hour never convert exactly, either — 1.67 hours at $90 comes to $150.30 — which is one more reason to bill in 6- or 15-minute increments.
Handle travel, overtime, and different rates
Decide in advance whether travel time is billable, and at what rate. Many trades bill travel at the full rate while many consultants charge half or nothing, and if evenings or weekends cost more, state the multiplier — time and a half, say — in the agreement.
When different work carries different rates, give each rate its own line. "Senior developer, 12.5 hours at $140" and "Junior developer, 20 hours at $85" are clearer than one blended rate the client can't check.
Write line items the client can verify
Group hours by task or by week, and describe the work, not just the time. "Kitchen rewiring, 7.5 hours" or "Homepage redesign, rounds 2 and 3, 6.25 hours" beats a single line reading "Services, 40 hours".
State the period covered and, for longer engagements, attach or offer a timesheet summary with dates and tasks. If the client approved an estimate or a not-to-exceed cap, show hours to date against it so there's no surprise as you approach the limit.
A worked example
A consultant billing October at $120 an hour might show three lines: "Discovery workshop, 3 October, 3.5 hours" ($420), "Findings report, 6 to 10 October, 11.25 hours" ($1,350), and "Client calls, 0.75 hours" ($90). That's 15.5 hours and $1,860 in total.
Every figure can be checked against the timesheet, every task is named, and the client can see where the time went without asking. That's what gets an hourly invoice approved on the first read.
Choose a billing rhythm
Long hourly engagements are easier on both sides when billed weekly or monthly rather than at the end. Smaller, regular invoices get approved faster, keep your cash flowing, and surface any disagreement about hours within a week or a month, not three months in.