Customers usually don't receive invoice emails because the address on file is wrong, the email has gone to their junk folder, or it reached someone who doesn't pay the bills. Check the customer's address and the delivery status in your accounting software first. If invoices keep landing in junk, ask whoever runs your email to set up SPF, DKIM and DMARC for your domain, including any software that sends email in your name.
In this article
The short version
- Check the email address on the customer record first.
- Look at the delivery status in your accounting software.
- Send to the person who pays, not the person who booked.
- Set up SPF, DKIM and DMARC, including for software that sends as you.
- Add a second channel such as SMS or WhatsApp.
Five checks to run first
You can rule out the usual causes in a few minutes. Work through these in order before you look at anything technical.
- Look at the email address on the customer record. A typo, an old address or a contact who's left the company will stop the invoice reaching anyone. If your software also holds an address in its company settings, check that one too.
- Check the delivery status in your accounting software, which usually shows whether an invoice email was sent or bounced. If you've added several recipients to one invoice, one failed address can show as a delivery problem for the whole invoice.
- Ask the customer to look in their junk or spam folder. If the address is right and the invoice still hasn't turned up, this is the likeliest place.
- Confirm you're sending to the person who pays. The person who booked the job is often not the person in accounts, and an invoice can sit in their inbox while they're on holiday. Ask for an accounts payable address when you take a customer on.
- Make sure bounces come back to an inbox someone reads. If your invoices go from a no-reply address, or replies land in a shared mailbox nobody checks, you won't see the bounce message that tells you something's wrong.
Why invoices land in junk
When an email arrives, the receiving mail service checks whether it really came from the domain it claims to come from. Three records on your domain answer that question. SPF lists the servers allowed to send email for your domain. DKIM adds a signature to each message showing it came from you. DMARC tells the receiving service what to do with email that fails those checks, and sends you reports on it.
The National Cyber Security Centre recommends all three to stop other people sending email that pretends to be from you. They matter for invoices too. GOV.UK guidance notes that email from a domain without them may not work properly or may be treated as spam.
One setting that's easy to miss is the SPF record for software that sends on your behalf. If your accounting, job management or payments software sends invoices from an address on your domain, that software needs to be included in the record. Otherwise its email can look like a forgery to the customer's mail service, even though everything you send from your own inbox arrives fine. Whoever manages your domain or IT can check these records for you.
When a customer says the invoice never arrived
Start by confirming the address with them over the phone or by text, then resend. Ask them to add your sending address to their safe senders list, so the next invoice isn't filtered.
Then ask yourself whether it's one customer or several. One customer missing invoices usually points to their address or their filters. Several customers missing invoices, especially at different companies, point more towards your domain set-up, and it's worth raising with your email provider.
A customer who normally pays on time and has gone quiet may simply not have the invoice, so a quick check of the address at that point can save weeks of waiting.
Give customers a second way to get the invoice
Even with everything set up, some emails are likely to go astray, so it helps to have another route. Adfin sends payment links by email, SMS or WhatsApp, so a customer who never sees the email can still pay from a text. Adfin's collection agents, part of the paid Enhanced plan, can also vary the channel and timing of reminders within rules you approve.
For customers you bill regularly, you can take the inbox out of it altogether. With direct debit through Adfin, each invoice is collected on its due date, and a notice goes to the customer no later than three working days beforehand. A card on file is charged automatically, with the customer told one business day before.
Common questions
Why are my invoices going to spam? Often because your domain isn't set up with SPF, DKIM and DMARC, or because the software sending your invoices isn't included in your SPF record. A customer's own filter settings can also catch it, so ask them to check their junk folder.
How do I know if my invoice email bounced? Check the delivery status in your accounting software and look for bounce messages in the inbox your invoices reply to. If invoices go from a no-reply address, you might not see a bounce at all.
Why does my software say the invoice was sent when the customer never got it? Sent usually means the email left your software, not that it reached the customer's inbox. It can still be filtered into junk or held back by the customer's mail server after that.
What are SPF, DKIM and DMARC? They're records on your domain that let receiving mail services check an email really came from you. SPF lists approved senders, DKIM signs each message and DMARC sets what happens to email that fails.
Should invoices come from a no-reply address? It's better if they don't. A no-reply address hides bounces and customer questions, so a real address someone reads gives you a much earlier warning.
Can I send invoices by text or WhatsApp? Yes, many payment and invoicing tools can send a link to the invoice by SMS or WhatsApp. It's a useful second channel for customers whose email filters are strict.
Sources
- National Cyber Security Centre - Email security and anti-spoofing (accurate as of October 2026) https://www.ncsc.gov.uk/collection/email-security-and-anti-spoofing
- GOV.UK - Set up government email services securely (accurate as of October 2026) https://www.gov.uk/guidance/set-up-government-email-services-securely
- Adfin - Accept payments (accurate as of October 2026) https://www.adfin.com/accept-payments
