Before you send: a quick pre-flight check
Check the document before it goes out. Confirm the invoice identifier follows your applicable rules, the issue and due dates are correct, the amounts and tax treatment add up, the payment details are accurate, and the invoice names the correct legal entity. If a correction is needed later, use the process required by your jurisdiction instead of silently replacing an issued record.
Ask the client in advance which billing address or portal to use, whether a purchase-order reference is mandatory, and whether they require a structured format. The person who commissioned the work may not be the accounts-payable contact. Following the buyer’s accepted submission process reduces avoidable questions and delays.
Email, client portal, or mail: which should you use?
The right channel depends on the buyer and the law. Email works when the buyer accepts a human-readable attachment. Supplier portals collect the fields and references a larger organization needs. Structured e-invoicing sends machine-readable data through a network or platform and can be mandatory even when a PDF looks complete. Mail remains relevant where a contract or procedure calls for paper.
Use the required channel and keep its submission confirmation. A sent-email entry proves that you sent a message, not that the right person received or accepted the invoice. Portal acknowledgments and network statuses can provide stronger operational evidence, but their legal effect varies.
| Method | Useful when | Evidence to keep | Watch out for |
|---|---|---|---|
| Email with PDF | The buyer accepts attachments | Sent message and any acknowledgment | Wrong address, spam or attachment limits |
| Portal or e-invoice network | The buyer or law requires a structured process | Upload, validation and delivery status | Required PO, identifiers and data format |
| A paper document is requested | Copy and any tracked-delivery record | Transit time and address errors |
What should you write in the invoice email?
Keep the email short and include the facts needed to route the invoice: issuer, invoice number, amount, and due date. A descriptive subject line also makes the message easier to find.
Use a direct, courteous tone. Here is a template to adapt:
Subject: Invoice INV-2026-014 from [Your Business] - due September 10, 2026
Hi [Name],
Please find attached invoice INV-2026-014 for [brief description of work], totaling USD 1,200, due on September 10, 2026.
Please follow the verified payment instructions on the invoice and use INV-2026-014 as the reference. If a purchase-order reference or correction is needed, please let me know.
Best regards, [Your name]
- A descriptive subject line
- Include your business name, the invoice number and the due date so the email is easy to spot and search for later.
- The invoice number and amount
- State both in the body so the client has the headline facts without opening the attachment.
- The due date in plain words
- Give an actual calendar date, not just net 14, so there is no ambiguity about when payment is expected.
- How to pay and the reference
- Point to the bank details on the invoice and ask the client to use the invoice number as the payment reference.
- A polite line for questions
- Invite the client to flag a missing PO number or any correction, which heads off silent delays.
How to attach the invoice as a PDF
When email is the accepted channel, a PDF preserves the intended page layout and reduces accidental editing compared with an editable source file. It is not tamper-proof and does not replace a structured e-invoice where one is required.
Use a recognizable file name such as Invoice-INV-2026-014-YourBusiness.pdf. Check the generated pages, totals, and payment details before attaching them. FreeBillGen produces a PDF from the completed draft, but the sender remains responsible for the inputs and delivery channel.
Retain the issued version and submission record for the period required by the applicable tax and company rules. The exact copy sent also supports later correction and reconciliation.
How do you follow up on an unpaid invoice?
Start by checking whether the invoice reached the required channel, passed validation, included the correct references, and is subject to a genuine dispute. Use the reminder and escalation timing in the agreement, the buyer's process, and applicable law rather than assuming one cadence fits every customer.
Keep reminders factual. Restate the invoice number, balance, and due date, attach or link the issued copy, and ask for the payment status or reason it is blocked. Refer only to interest, fees, suspension, or recovery steps that the contract and law support. Preserve each message and response.
- Before the due date, if appropriate
- Use a pre-due reminder only when it fits the agreement and relationship; confirm the reference, amount, and due date.
- After the due date
- Verify acceptance and send a factual overdue note through the agreed channel, with the issued copy available.
- If payment is still blocked
- Ask for the reason, responsible contact, and expected payment date, and correct a valid routing or document issue through the proper process.
- Further escalation
- Follow the contract and local notice rules before referring to interest, fees, service suspension, or a formal demand.
- Recovery action
- Use a statutory, court, or collection route only after checking the governing law, evidence, amount, and required notices.
Sending an invoice: common questions
What is the best way to send an invoice?
Use the channel the client and applicable rules accept. Email with a PDF is convenient for many buyers, while larger organizations and public bodies may require a supplier portal or structured e-invoice. Ask before billing and keep the submission acknowledgment.
Should I send an invoice as a PDF or a Word document?
If the buyer accepts an email attachment, PDF preserves the intended page layout and reduces accidental editing compared with an editable source file. It is not tamper-proof and is not a substitute for a required structured e-invoice. Send an editable source file only when the agreed process calls for it.
What do I write in the email when sending an invoice?
Keep it short and complete. Use a subject line with your business name, the invoice number and the due date, then in the body thank the client, state the invoice number, the amount and the due date in plain words, explain how to pay and which reference to use, and invite them to flag any missing purchase-order number or other issue.
Who should I address the invoice email to?
Send it through the contact or channel the client has designated for accounts payable, which may differ from the person who hired you. Ask early who processes invoices and whether a purchase-order number is required. A missing required reference or the wrong recipient can delay acceptance and payment.
How soon should I follow up on an unpaid invoice?
Use the timing in the agreement, buyer process, and applicable law. After the due date, first verify that the invoice was accepted and is not under a genuine dispute. Then send a factual reminder with the invoice number, balance, due date, and issued copy, and ask for the payment status or reason it is blocked.
Can I charge interest on a late invoice?
A contract or statute may allow interest or recovery costs for a qualifying overdue debt. Contractual charges normally need advance agreement, while statutory rights can have their own scope and conditions. Check the governing law, debtor type, rate and notice rules before charging.