LetterAgent
Mail physical letters by just asking your AI assistant.
Yes. A faxed invoice works when it carries the invoice number, the amount due, the due date, and clear payment instructions on a single readable page. Fax suits customers and accounts departments that still file on paper, but keep a second copy for your own records.
| Invoice element | Why the recipient needs it |
|---|---|
| Invoice number and date | Accounts can match payment to the right invoice without calling you |
| Seller and buyer names and addresses | Proves who billed whom, and where records should be filed |
| Item lines with quantities and rates | Buyer can check the charge before paying, reducing disputes |
| Total due and currency | Removes doubt about the exact amount and its currency |
| Due date and payment terms | Sets the payment clock running from a clear date |
| Payment instructions | Tells the buyer how to pay: cheque, transfer, or another method |
Keep the invoice to one page when you can, and never let a totals row fall alone onto page two. Use a font size of at least 11 points for amounts, dark black text, and clear column headings. Avoid light grey shading behind totals, since fax turns shading into a muddy block that can hide the figure underneath. If your invoice template uses colour to separate sections, replace that separation with bold headings or ruled lines for the fax version. A buyer who cannot read the total will not pay on time, and a buyer who misreads it will pay the wrong amount, which creates a second round of paperwork for both sides.
State the terms in plain words on the invoice itself, not just in a separate email. Common terms include payment due on receipt, due within a set number of days, or due by a named date. Spell out the month for any date, so "March 5, 2026" cannot be misread across date formats. Add any late-payment policy only if it was agreed in advance, and state it briefly: a one-line note beats a paragraph of fine print that fax resolution will blur. If you offer a discount for early payment, state the discount, the deadline, and the discounted total, so the buyer does not have to do the arithmetic.
Payment instructions deserve the same clarity. Give the payee name exactly as it should appear on a cheque or transfer, and give one primary payment method first, with alternatives second. Never put full bank account details on a faxed invoice if a safer method exists: many businesses print only the details needed for the chosen method, and share fuller banking details through a secure channel on first setup. In Canada, note the applicable sales tax as its own line, as Canadian invoices commonly do; in the US, note any sales tax only where it applies to the sale.
Match the customer's accounts process. Some accounts departments still file paper invoices and will process a fax faster than an emailed PDF that sits in a shared inbox. Others run entirely on emailed invoices and will delay a fax while someone scans it. When in doubt, ask the customer which channel their accounts team prefers, and note the answer on the customer record so the next invoice goes the same way. Sending both a fax and an email without labelling one as the record copy creates duplicate-payment risk: an accounts clerk may pay twice, once from each copy. If you send both, mark one "Record copy" and the other "Copy for convenience" or similar, so only one is paid.
Keep the fax confirmation page with your copy of the invoice, filed under the invoice number. That pair is your proof of send date and page count if a customer later says the invoice never arrived. For larger amounts, add one confirmation step: a brief call or message a few days after sending, asking whether the invoice reached accounts and whether anything is unclear. That check often surfaces a misrouted fax before the due date passes, while there is still time to resend. LetterAgent fax is available in testing for US and Canadian numbers, with a per-fax quote and a page count verified before you approve the total, which gives you a clean page count to match against the confirmation.
Ready to fax it? Fax with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is sent.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
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