How to send
an invoice

Writing an invoice is half the job. The other half is getting it in front of the person who can pay it, in a form their system accepts, with nothing left to query. Most late payments start here: an invoice sent to the wrong inbox, missing a purchase order, or without a clear date.

Send it promptly

Payment terms usually count from the invoice date, so a 30-day term on an invoice you send a fortnight late is really a six-week wait. Send the invoice the day the job finishes, or on the dates you agreed for staged or monthly work. If no payment date was agreed at all, the law treats a business customer's payment as late 30 days after they receive the invoice or the goods or service, whichever is later; the clock does not start until the invoice arrives.

Email it as a PDF

Email is the normal way to send an invoice, and a PDF is the safest format: it looks the same on every screen and the figures cannot be edited by accident. Name the file clearly, for example "INV-0042 Smith Joinery.pdf", so it stays findable in the customer's system.

Some larger customers ask for invoices through a supplier portal or in a structured electronic format. Follow their instructions exactly; an invoice sent outside the process they gave you can sit unpaid for weeks. From April 2029 every VAT invoice will have to be issued as an e-invoice, which the e-invoicing guides explain.

Send it to the right person

The person you did the work for is rarely the person who pays invoices. Ask at the start who should receive them, usually an accounts payable address, and copy your contact so they know it has gone. If the customer uses purchase orders, quote the number on the invoice and in the email.

What to write in the message

Keep it short and put the facts first:

• Subject: "Invoice INV-0042 from Smith Joinery, £390.00, due 28 March"
• Body: one sentence saying what the invoice is for, the amount, the due date and how to pay, with the invoice attached
• Sign-off: your name and a phone number for queries

Ask the customer to use the invoice number as the payment reference. It makes matching the payment to the invoice quick for both of you, and a remittance advice from them will quote it.

Posting a paper invoice

Post is still fine if the customer prefers it. Send it first class, keep a copy, and note the date of posting. For a large invoice, consider sending it by a signed-for service so there is no doubt about when it arrived.

After you send it

Record that the invoice was sent, when and to whom, and diary the due date; the invoice due date calculator works it out for any term. A short, friendly reminder a few days before the due date prevents many late payments. If the date passes, the guide on chasing an unpaid invoice sets out what to do next, step by step.

Common reasons invoices are not paid

Most delays are avoidable. The invoice went to someone who does not process payments. It is missing a purchase order number. The customer's name on the invoice does not match their supplier record. The bank details are missing or unclear. Or the invoice arrived as an editable document the customer's system rejected. Fix those five and most invoices are paid when they should be.

Sending invoices for regular work

For a customer you work for every month, agree a rhythm: an invoice on the last working day of each month, or on the same date every month. A predictable invoice lands in a predictable payment run. Say in your first invoice when the next one will come, and keep the description consistent so the customer's approver recognises it straight away.

Choosing how to send

Each way of sending has a place. Pick the one that gets the invoice into the customer's payment process fastest, and keep evidence that it arrived.

Timing: why the day you send matters

Payment terms normally run from the invoice date, and where no date was agreed the law runs 30 days from when the customer receives the invoice or the goods or service, whichever is later. Either way, a late invoice means a late payment. The chart shows how the wait stretches when an invoice on 30-day terms goes out late.

If you want a predictable rhythm, invoice on the same day every week or month for ongoing work, and immediately for one-off jobs. The invoice due date calculator shows the date each term produces.

Getting through a customer's approval process

Larger customers run invoices through a sequence: receipt, matching to a purchase order, approval by the budget holder, then a scheduled payment run. An invoice that fails any step goes back to the start. To pass first time:

• Ask at the outset who receives invoices and whether a purchase order is needed.
• Quote the purchase order number exactly, on the invoice and in the email subject.
• Use the customer's registered name, the one on their supplier record.
• Match your description and amounts to the purchase order line by line.
• Ask when their payment runs happen, and time your invoice to arrive before one.

A reminder schedule that works

Sending is not finished until the invoice is paid. A light-touch schedule catches most problems before they become late payments:

Beyond that, the guide on chasing an unpaid invoice covers statutory interest and letters before action, and the guide on charging interest on late payments explains the rules for business customers.

If an invoice bounces or goes missing

An email that bounces, or an invoice the customer says never arrived, is best fixed the same day. Confirm the right address by phone, resend with the original invoice date and number (not a new one), and note the resend in your records. If the customer's terms run from receipt, agree with them in writing which date the terms now run from, so there is no dispute later about when payment became late.

Sending invoices to individuals

For a household customer, keep it simple: a clear PDF, a friendly email, the amount, the due date and how to pay. Many households prefer to pay by bank transfer on the day the invoice arrives, so a payment link or clear bank details make a real difference. The Late Payment Act does not apply to consumers, so agree your terms before you start. See invoice payment terms.

Keeping a record of sending

Keep the sent email, or a note of the posting date, with the invoice. If the customer later says they never received it, the record settles it, and if the debt ever reaches a letter before action or a small claim, it shows when the payment clock started. Your invoices and the evidence around them are part of the records you must keep; see how long to keep invoices.

Getting ready for e-invoicing

From April 2029 every VAT invoice will have to be issued as an e-invoice: structured data that goes straight into the customer's system, not a PDF. If you are VAT registered, sending by email will change. In June 2026 the government announced that Peppol will be the core interoperability network; the detailed standards and milestones are due in a roadmap at Budget 2026. The e-invoicing hub tracks what is known, and the guide on e-invoices versus PDF invoices explains the difference.

A sending checklist

Before you press send, check five things. The invoice is a PDF with a clear file name. It is addressed to the person or inbox that pays invoices. The subject line carries the invoice number, amount and due date. Any purchase order number is quoted. And your own record shows the date and time it went. Five checks, thirty seconds, and most of the reasons invoices sit unpaid are gone.