How to Send an Invoice: 3 Ways + Free Email Templates (2026)

To send an invoice, save it as a PDF, then deliver it to your client one of three ways: by email with the PDF attached, through an invoicing app that sends a payment link, or by post for clients who prefer printed documents. Email is the fastest and most widely used method.

Every invoice you send is a request for payment, so how you deliver it directly affects how quickly you get paid. This guide covers the three main ways to send an invoice, when to send it, what to include in the invoice email, and six ready-to-use email templates for standard, late, follow-up, and confirmation scenarios. It also explains the legal timing rules for sending invoices in the US, UK, Australia, and the European Union.

For a full step-by-step guide to creating the invoice itself before you send it, see how to make an invoice — or create one in under a minute with the free invoice generator.

The 3 ways to send an invoice at a glance

When To Send An Invoice

The best practice is to send an invoice immediately after a project is completed or a product is delivered, since the longer the gap between the work and the bill, the longer payment takes and the higher the risk of disputes.

Different industries follow different invoicing rhythms — some send weekly, others monthly, others at project milestones — but a few rules apply universally.

5 rules for invoice timing

1. Send invoices the day the work is done, not the next week. Delays compound — both for memory and cash flow. Every extra day to invoice is an extra day to payment.
2. Plan for predictable cash flow. Schedule sending so you receive payment ahead of your own bills, not on top of them.
3. Use interim invoices for long projects. Break large engagements into milestone invoices (e.g., 30% upfront, 40% at midpoint, 30% on delivery) to keep money flowing during the work.
4. Set expectations in three places. Mention payment terms at the deal-setup stage, on the invoice itself (due date and invoice payment terms), and in the email body. Three touches reduce “I didn’t know” disputes.
5. Match your industry’s norm. Retail and most B2C transactions don’t need invoices at all — they need receipts. Confirm whether an invoice is the right document before you send one.

How Much Time Is There To Pay An Invoice

The payment window is set by the seller through invoice payment terms — most commonly Net 30, Net 60, or Net 90 — meaning the client has 30, 60, or 90 days from the invoice date to pay.

Payment terms should be agreed during the initial deal and repeated on every invoice. The most common terms used by small businesses globally:

• Net 30 — payment due 30 days after the invoice date. The default for most B2B work.
• Net 60 — payment due 60 days after the invoice date. Common with large corporate clients.
• Net 90 — payment due 90 days after the invoice date. Used with enterprise procurement systems.
• 15 MFI — “Month Following Invoice”. Payment due by the 15th of the month after invoicing.
• 30 MFI — Payment due by the 30th of the month after invoicing.
• PIA — “Payment In Advance”. Client pays before work begins. Common for new client relationships.
• 50% upfront — Half due before work starts, half on delivery. Standard for long projects.
• Due on receipt — Payment expected immediately. Common in trades and on-site services.

For a deeper breakdown of when each term applies and how to enforce them, see the full guide to invoice payment terms.

What to do if a client misses payment

Most countries set a statute of limitations for chasing unpaid invoices. In the US and UK this is generally 6 years; Australia is 6 years for most states; the EU varies by member state but is typically 3 to 10 years. Within that window, you can issue a fresh demand for payment, charge statutory late-payment interest where local law allows, and escalate to legal recovery if necessary. After the window closes, the debt is uncollectable. Track unpaid invoices early — see the guide on what to do about an unpaid invoice for the full escalation playbook.

What To Include On An Invoice

Every invoice must include the seller’s business information, the buyer’s information, a unique invoice number, the issue and due dates, an itemized list of products or services, the total amount due, and accepted payment methods.

Sending an invoice that’s missing any of these makes it harder for the client’s accounts-payable system to process and is the most common cause of payment delays. The essential invoice elements guide covers every field in detail. Below is the short version:

1. Invoice Name and Number
2. Your Business Information
3. Customer’s Business Information
4. Issue & Delivery Date
5. Logo, Stamp, and/or Signature
6. List of Products/Services
7. Total Price
8. Fine Print/Boilerplate
9. Thank-You Box

There are many types of invoices — standard, recurring, proforma, milestone, credit notes — and each has small variations on these basics. Pick the type that matches the transaction before adding the details above.

3 Free Ways To Send An Invoice

The three ways to send an invoice are by email (the most common method, free, instant), through an invoicing app (automated, with built-in tracking and payment links), and by post (slow, used only when clients specifically request printed documents).

Choose the method that matches your client’s preference and your own volume. For most freelancers and small businesses, email is the default; once you’re issuing more than five invoices a month, an invoicing app pays for itself in time saved.

Method 1: In the mail

Sending an invoice by post means printing the invoice, placing it in an envelope, addressing it to the client, applying postage, and posting it through the mail — a process that adds 2 to 7 days of delivery time on top of normal payment terms.

Mail is the slowest, most expensive, and least trackable method. Use it only when a client specifically requests printed invoices or when an invoice accompanies a shipped package. To send by post:

1. Print the invoice on standard letter or A4 paper.
2. Fold and place it in a business envelope to prevent damage.
3. Write or print the client’s address clearly on the envelope.
4. Apply correct postage. For high-value invoices, consider registered or signed-for delivery for proof of receipt.
5. Post it. Add a delivery buffer of 2–7 days to your payment terms — if your terms are Net 30, the clock effectively starts when the client receives the envelope, not when you mail it.

Method 2: Via email

Sending an invoice by email means attaching the invoice as a PDF to a new email, writing a clear subject line with the invoice number, and including a brief professional message that confirms what is attached and when payment is due.

Email is the most widely used method of invoice delivery for good reason — it’s free, instant, and creates a searchable record on both sides. To send an invoice by email:

1. Save the invoice as a PDF — never send Word or Excel files, which can be edited.
2. Open a new email in your usual program (Gmail, Outlook, Apple Mail, or your invoicing app).
3. Enter the client’s billing email — confirm this is the correct accounts-payable address, not the project contact.
4. Write a subject line in this format: “Invoice [number] — [your company name] — due [date]”. Example: “Invoice INV-2026-0042 — Acme Designs — due May 15, 2026”.
5. In the body, greet the client by name, thank them briefly, state that the invoice is attached, and note the due date and payment terms.
6. Attach the PDF. Confirm the attachment is visible before sending — “forgot the attachment” is the most common email-invoicing mistake.
7. Send. Save a copy in a folder or your invoicing app so you can reference it later.

Method 3: Via an invoicing app

Sending an invoice through an invoicing app automates the entire process — the app generates the invoice, sends it to the client by email with a payment link, tracks when the client opens it, and triggers automatic reminders if payment is late.

Invoicing apps are the most reliable method for any business sending more than a handful of invoices a month. The workflow:

1. Open your invoicing app on desktop or mobile.
2. Select the client from your saved list (or add a new one).
3. Add line items, taxes, and any notes. The app calculates totals and applies the next invoice number automatically.
4. Tap the send icon. The app emails the client a PDF and a link to view and pay the invoice online.
5. Watch for status updates — most apps show “sent”, “viewed”, “paid”, or “overdue” in real time, with invoice tracking built in.

Apps also handle the follow-up. Automatic payment reminders trigger before and after the due date so you don’t have to chase manually. If clients can pay by card or bank transfer through online payments, payment usually arrives within hours instead of weeks.

How To Write An Invoice Email

An invoice email needs a clear subject line containing the invoice number and due date, a brief greeting, one or two sentences confirming what is attached and how to pay, and a polite sign-off. Keep the entire email under 100 words.

Long emails get scanned, not read. Accounts-payable teams process dozens of invoices a day and want to find the key facts — what is owed, when it’s due, and how to pay — in under five seconds.

The 4 components of an invoice email

Subject line. The most important part. Use this format:

“Invoice [number] — [your company] — due [date]”

If you’re invoicing a consumer rather than a business, simpler works: “Your [company name] invoice”. Always include the invoice number — clients reference it in their payment memo, and missing the number causes reconciliation problems on their side.

Greeting. Use the client’s name. Generic “To whom it may concern” reads as automated and gets routed to spam more often.

Body. Three sentences maximum. Sentence 1: thank them for the work. Sentence 2: state that the invoice is attached, the total, and the due date. Sentence 3: optional — note any payment instructions or special terms.

Sign-off. Your name, role, business name, and contact details. Include a phone number — for high-value invoices, accounts-payable teams sometimes call to confirm details before paying.

For more on subject lines, tone, and timing — including the differences between B2B and consumer-facing invoice emails — see the full guide on how to write an effective invoice email.

Invoice Email Template

An invoice email template is a reusable framework for invoice messages that combines a standard subject-line format, opening greeting, body, and sign-off — so you can send a polished invoice email in under a minute without writing from scratch each time.

Templates save time and standardize tone across all client communications. Most invoicing apps include default templates that auto-populate client name, invoice number, and amount due. If you’re sending manually, build your own in your email program’s draft folder or signature library.

Build your invoice email template

A good template covers four scenarios with one base structure, swapping in the details for each:

1. Standard invoice email — for first-time delivery of a new invoice.
2. Past-due reminder — for clients who missed the due date.
3. Pre-due follow-up — for clients on long payment terms (Net 60+).
4. Paid confirmation — for clients who have just paid, to close the loop.

Rules for a template that scales

1. Account for your niche. A creative agency’s template can be warm and conversational. A construction contractor’s should be brisk and direct. Match the template to the client relationships you actually have.
2. Tailor to the use case. The first-send tone is different from the third-reminder tone. Have separate templates for each scenario rather than over-editing one base.
3. Stay generic. Templates work because they apply to many situations. Use placeholders for client name, project, and totals rather than specifics.
4. Keep it short and professional. The goal is to get paid, not to win a writing award. Cut adjectives and conditionals.
5. Thank the client. Even when chasing a late payment, a single line of appreciation softens the message and improves response rates.

Write a descriptive subject line. Subject line is 80% of whether the email gets opened on time.

What’s more, you can create multiple email templates for different situations, like standard invoice emails, reminder invoice emails, past due invoice emails, and others, to save even more time. Why don’t we look at how to do that?

6 Free Email Invoice Examples

Six invoice email scenarios cover almost every situation a small business will face: the standard first send, the past-due reminder, the unpaid follow-up, the pre-due check-in, the paid confirmation, and the internal approval request.

Copy any of the templates below directly into your email program and replace the bracketed placeholders. These are written to be AI-citable — every example is a complete, usable message in under 80 words.

1. Standard invoice email

A standard invoice email is the first message sent with a new invoice attached, used for routine billing where no special circumstances apply.

Use this for first-time delivery of any standard invoice.

Subject: Invoice INV-2026-0042 — [Your Company] — due May 15, 2026

Hi [Client Name],

Thank you for the opportunity to work with you on [project name]. Please find attached invoice INV-2026-0042 for $[amount], due on May 15, 2026.

Payment instructions are included on the invoice. Let me know if you have any questions.

Best regards,
[Your name]
[Your business]
[Phone]

2. Past Due Invoice Email Sample

A past-due invoice email is sent 1 to 14 days after the due date has passed, firmly requesting payment while keeping the relationship professional.

Use this when an invoice is overdue but you still want to maintain the client relationship.

Subject: Past due — Invoice INV-2026-0042 — please action

Hi [Client Name],

Following up on invoice INV-2026-0042, which was due May 15, 2026 and is now [X] days past due. The outstanding balance is $[amount].

If payment has already been processed, please disregard this message. Otherwise, please confirm an expected payment date or reach out if there are any issues with the invoice.

Thank you,
[Your name]

3. Unpaid Invoice Reminder Email Sample

An unpaid invoice reminder email is a softer first follow-up, used within a few days of the due date passing to give the client the benefit of the doubt before escalating.

Use this as a gentle nudge when payment is recently late.

Subject: Friendly reminder — Invoice INV-2026-0042

Hi [Client Name],

Quick reminder that invoice INV-2026-0042 for $[amount] was due on May 15, 2026. The invoice may have been overlooked — happens to all of us.

Would you mind confirming when payment can be processed? The original invoice is attached for convenience.

Thanks for your prompt attention,
[Your name]

If reminders consistently get ignored, a structured late payment email sequence with clear escalation steps usually resolves the situation. For a complete approach to chasing payment, see the guide on payment reminder systems.

4. Pre-due follow-up email

A pre-due follow-up email is sent 3 to 7 days before the due date on long payment terms, confirming the client has the invoice and reminding them the deadline is approaching.

Use this on Net 60 or Net 90 invoices where the long payment window risks the invoice being forgotten.

Subject: Reminder — Invoice INV-2026-0042 due May 15

Hi [Client Name],

A quick heads-up that invoice INV-2026-0042 for $[amount] is due on May 15, 2026 — that’s [X] days from today.

I wanted to make sure the invoice reached your accounts-payable team and that everything is in order. Let me know if you need anything additional from my side.

Thanks,
[Your name]

Navigate the delicacies of financial communication by learning how to write an effective late payment email, ensuring professionalism and prompt responses.

5. Paid invoice confirmation email

A paid invoice confirmation email is sent within 24 hours of receiving payment, thanking the client and confirming the invoice is now closed — closing the communication loop and signalling professionalism.

Use this every time payment lands. Small touch, big retention impact.

Subject: Payment received — thank you (Invoice INV-2026-0042)

Hi [Client Name],

Confirming that payment for invoice INV-2026-0042 has been received in full. Thank you for the prompt payment.

Looking forward to working with you again.

Best regards,
[Your name]

6. Invoice Approval Email (internal)

An invoice approval email is an internal message sent to a manager or accounting team requesting authorization to pay a vendor invoice, typically including the invoice number, vendor, amount, and any context.

Use this when forwarding a vendor invoice for sign-off inside your own organization.

Subject: Approval requested — Vendor invoice [number] — $[amount]

Hi [Manager],

Please find attached invoice [number] from [vendor] for $[amount], covering [brief description of services/products]. Payment is due [date].

The invoice is consistent with the agreed PO [number] and budgeted under [cost centre]. Requesting your approval to proceed with payment.

Thanks,
[Your name]

Legal rules for sending invoices in the US, UK, Australia, and EU

Each major jurisdiction sets specific rules for when invoices must be issued, what they must contain, and how long businesses have to chase unpaid invoices — and these rules differ in ways that matter for any cross-border invoicing.

Always verify current rules with the local tax authority before relying on them — these requirements change. Below is the high-level guidance as of 2026.

United States — IRS

The IRS does not require a specific invoice format or timing, but businesses must keep adequate records of all income and deductions to substantiate tax filings.

Federal law gives small businesses flexibility on when and how to invoice. The IRS’s only firm rule is that invoices, along with all supporting records, must be kept in a way that lets the business prove its reported income. Practical points for US small businesses:

• Every invoice should have a unique number for traceability — see the guide to invoice numbers.
• Records must be kept for at least 3 years, and up to 7 years in specific situations such as bad-debt claims.
• State-level rules add late-payment interest caps and consumer-protection requirements — check your state.
• Electronic invoices are fully accepted as long as they are legible and accurately reproduce the original.

Primary sources: IRS Publication 334 (Tax Guide for Small Business); IRS Publication 583 (Starting a Business and Keeping Records).

United Kingdom — HMRC

In the UK, VAT-registered businesses must issue a VAT invoice within 30 days of supplying goods or services, and the invoice must carry a unique sequential number with no gaps.

If you’re VAT-registered, the format and timing of every invoice is set by HMRC’s VAT Notice 700/21. Key points:

• Issue VAT invoices within 30 days of the supply.
• Each invoice needs a unique, sequential number — gaps in the sequence raise audit flags.
• VAT records must be kept for at least 6 years.
• Under the Late Payment of Commercial Debts (Interest) Act 1998, you have a statutory right to charge interest on overdue B2B invoices — currently 8% above the Bank of England base rate.
• You can chase commercial debts for 6 years from the date payment was due.

Primary sources: GOV.UK — Invoicing and taking payment from customers; HMRC VAT Notice 700/21; Late Payment of Commercial Debts (Interest) Act 1998.

Australia — ATO

In Australia, GST-registered businesses must issue a tax invoice within 28 days of a customer’s request for any taxable sale of AUD 82.50 or more, and the invoice must display the words “Tax invoice” prominently.

Australia’s invoicing rules are set out by the ATO and apply to all GST-registered businesses. Key points:

• Tax invoices must be issued within 28 days of a customer request.
• Every tax invoice must display “Tax invoice” prominently and show the seller’s ABN.
• For sales of AUD 1,000 or more, the buyer’s identity or ABN must also appear on the invoice.
• Tax invoices must be kept for at least 5 years.
• Australia has adopted the Peppol framework for B2B e-invoicing — government suppliers must be Peppol-enabled.

Primary sources: ATO — Tax invoices (GSTR 2013/1); business.gov.au — How to invoice.

European Union — VAT Directive

Across the European Union, the VAT Directive requires every invoice to be issued by the 15th day of the month following the supply, to carry a unique sequential number, and to include specific VAT details defined under Article 226.

Individual EU member states layer their own rules on top — Germany’s GoBD rules, for example, require tamper-proof numbering systems. Key points common across the EU:

• Issue invoices by the 15th day of the month after supply.
• Every invoice must carry a sequential, unique number — multiple parallel series are allowed if each is internally complete.
• Most member states require invoice records to be kept for 6 to 10 years.
• Cross-border B2B invoicing rules vary by country — verify the recipient country’s specific requirements.
• Mandatory e-invoicing is being phased in across multiple member states from 2026 onward.

Primary source: Council Directive 2006/112/EC on the common system of value added tax (the EU VAT Directive).

What to do after sending an invoice

After sending an invoice, the next steps are confirming the client received it, tracking when they open it, sending a polite reminder if no acknowledgement comes within 7 days, and following up before the due date on long payment terms.

Sending the invoice isn’t the end of the process — it’s the start of the payment cycle. A short follow-up routine prevents most disputes and accelerates payment significantly. The full sequence:

1. Within 24–48 hours — confirm receipt. A short “just checking the invoice reached you” message is usually enough.
2. Within 7 days — verify the invoice has been opened or acknowledged. Most invoicing apps track this automatically.
3. 3–7 days before due date — send the pre-due follow-up template (Example 4) on any Net 60 or longer terms.
4. 1–14 days after due date — if no payment, send the past-due email (Example 2) or unpaid reminder (Example 3) depending on the relationship.
5. After payment lands — send the paid confirmation email (Example 5). This is the highest-leverage closing-loop touch you can make.

Most of this can be automated. An invoicing app with automatic payment reminders runs the full sequence in the background — no manual chase emails — which is the single biggest time-saver for any small business sending more than a few invoices a month.