Show the work, not the diary
Group time by task or by day, not by every interruption. "Payment integration — 11.5 h" is checkable. Forty entries of fifteen minutes each invites a line-by-line audit, and the client who does that is not questioning your honesty, they are doing the job your invoice asked them to do.
Round consistently, and say how
- Pick an increment — six minutes, a quarter hour, half an hour — and use it everywhere
- State the increment in your terms, so it is a policy rather than a per-entry decision
- Round the same way for short tasks as for long ones
- Never round a total after rounding the lines it is made of
Handle overruns before the invoice, not on it
An estimate exceeded by half is a conversation, and the invoice is the worst place to have it. Agree a cap or a checkpoint at the start; when you reach it, say so then. An invoice that carries the first news of an overrun rarely gets paid on time.
Bill on a rhythm
For ongoing hourly work, invoice fortnightly or monthly rather than at the end of a project. It keeps the amounts small enough to approve without escalation, and it surfaces a dispute while there are still hours left to adjust.
Common questions
- Should I attach a timesheet?
- Attach it if the contract requires it or the client asks. Otherwise summarise on the invoice and keep the detail ready — offering a level of detail nobody requested invites scrutiny you did not need.
- Do I bill for travel time?
- Only if you said you would, in advance, and at whatever rate you agreed. Travel appearing on an invoice for the first time is one of the most reliably disputed lines there is.
- How do I bill part hours?
- In your stated increment, rounded consistently. What matters far more than the increment you choose is that the same rule is visible on every invoice you send.