How to Invoice Clients by the Hour: Examples for UK Freelancers

Hourly invoicing sounds easy: multiply your time by your rate. In practice, disagreements start with what counts as billable and how small blocks of time are rounded.

A clear hourly invoice starts long before the PDF is created. It starts with an agreed rate and a record of the work.

Agree what the hourly rate covers

Before you begin, confirm the rate, the type of work included and whether there is a maximum number of hours. Also agree how you will handle meetings, travel, research, testing and requests outside the original scope.

"Website development at £65 per hour, up to 12 hours without further approval" is more useful than an informal agreement to charge "by the hour". If the work is likely to exceed the cap, ask before continuing. An accurate invoice does not settle a disagreement about work the client never approved.

How to calculate an hourly invoice

The formula is hours worked × hourly rate = the amount before any applicable tax. At £65 per hour, 12.5 hours is £812.50, because half an hour is 0.5 of an hour, not 0.30.

The total is clear, and the client can recognise the work completed.

Converting minutes into decimal hours

Many time trackers record minutes, while invoices calculate amounts using decimal quantities. Common conversions:

If you worked for 1 hour and 45 minutes, enter 1.75 hours. Entering 1.45 hours would understate the time. Choose a clear rounding policy in your agreement: some businesses bill in 15-minute increments, others use precise recorded time. Avoid quietly rounding every task up without telling the client.

How detailed should the invoice be?

It depends on the relationship. For a small monthly retainer, a single agreed service line may be enough. For unpredictable development work, two or three grouped descriptions are often clearer.

• Too vague: "Technical work, 12.5 hours."
• Better: "Website maintenance, CMS updates and responsive layout fixes, 12.5 hours."
• Most useful where the client needs detail: separate lines for development, content changes and testing, with the hours assigned to each.

You can send a detailed time log separately if the client wants it. The invoice should summarise what they are paying for, not force them to read an entire timesheet.

What about meetings and administrative work?

Billable activity should follow the contract. If discovery meetings, project management or research are included in the rate, say so in advance. If not, do not add them later without agreement. The same applies to urgent or out-of-hours work: agree any higher rate before the work is done.

For repeat clients, a simple monthly time summary can prevent surprises and make invoice approval easier.

Include the ordinary invoice information

UK invoices still need a unique reference, supplier and customer details, invoice and supply dates, a clear description, amounts and a total, plus VAT information where applicable. Our guide to what a UK invoice must include has the full list. Add a payment due date and bank reference to make the invoice easier to process, and a purchase order number if the client requires one.

Next Invoice has flexible quantity and rate labels, including hours, and lets you group line items under section headers, which suits invoices with several types of work. Review the exported PDF before sending it.

A sensible monthly billing routine

Record time as you work rather than reconstructing it at month-end. Review the entries against the approved scope, correct accidental duplicates, group them into understandable descriptions and calculate the amounts. Then issue the invoice promptly, keep a copy with the project's time records and update the status when you confirm payment.

Hourly billing does not need to feel complicated. Clear terms, accurate arithmetic and recognisable descriptions make the difference between a routine invoice and an avoidable conversation about the bill.