If you are a sole trader, an invoice is not just a formality - it is the document that actually gets you paid, and it is often the first genuinely "professional" thing a new client sees from you. Getting it right matters more than most people think.
What a UK invoice legally needs
A unique invoice number that follows on from your last one, with no gaps or repeats
The invoice date and the date the goods or services were supplied (if different)
Your name or trading name, address and contact details
Your customer's name and address
A clear description of what was supplied, the quantity and the price
The total amount owed and, if you are VAT registered, the VAT amount and your VAT number
None of this needs a solicitor to get right - it is standard practice, and any decent invoicing tool (Invoito included) will structure this for you automatically so you can't accidentally leave something out.
When to send the invoice
The best time to send an invoice is the moment the work is done - not at the end of the month, not "when you get a chance". The longer the gap between finishing a job and asking to be paid for it, the easier it is for both of you to forget the details, and the longer you wait for your money.
Setting payment terms clients actually respect
State your payment terms on every invoice, not just in a conversation before the job. "Payment due within 14 days" printed clearly on the document gives you something concrete to point back to if a payment runs late - a verbal agreement gives you nothing.
Common terms for UK sole traders are 7, 14 or 30 days. Shorter terms are entirely reasonable, especially for smaller jobs or new clients - there is no rule that says you have to offer 30 days just because larger companies do.
The one habit that prevents most late payments
Send the invoice on the same day you finish the job, every time, without exception. It sounds too simple to matter, but the single biggest predictor of a late payment is a late invoice - clients pay what is in front of them, not what they remember owing.