Mail invoices and collection letters online
By Justin Winter · Updated September 16, 2026
The short answer
Small businesses can mail an invoice or past-due notice First-Class for $0.99 — and escalate to a Certified final demand for $12.99 — without a printer, from the browser or straight from their tools via API.
The math
The break-even on one letter.
$14.99 divided by the hours the errand takes is the hourly rate at which paperplane costs the same as your time. A 30-minute round trip, for example, breaks even at about $30 an hour. Use your own figures.
Usually the right pick: First-Class · $0.99, Certified for final demands
A paper invoice still gets paid. Plenty of customers — property managers, older clients, government offices — pay what lands in the physical inbox and let email invoices rot in spam. Mailing the invoice First-Class at $0.99 costs less than the time spent re-sending the PDF a third time.
For receivables, escalate in writing: a friendly First-Class reminder at 15 days, a firmer one at 30, and a Certified final demand ($12.99) at 60 stating the amount, the deadline, and what happens next (collections, small claims, mechanics lien — whatever genuinely applies). The Certified step routinely shakes out payment precisely because it signals you are building a dated record.
If you do end up in small claims, the sequence of dated letters is your case: it shows the debt, the demands, and the debtor’s silence. Lawful collection letters are explicitly allowed by screening; what is refused is harassment and threats you cannot lawfully carry out (do not threaten a lien you have no right to file).
Sending more than a few: prepaid credits add up to 35% bonus balance, and the REST endpoint (POST /v1/orders) means your invoicing tool or an agent can drop a letter in the mail when an invoice hits 30 days past due.
This page is general information about USPS mailing options, not legal advice. Notice rules vary by state and by document. Check your lease, contract or local rules, or ask an attorney, before relying on it for a deadline.
Questions before you send
Why not go to the post office myself?
You can. paperplane does not replace the post office; it replaces the trip. USPS still carries the letter. What you skip is the printer, the envelope, the stamp and the walk to a mailbox. $0.99 covers all of it.
If something goes wrong, do I pay?
If we cannot mail the letter, the hold on your card is released and you are not charged. If a letter fails after your card is charged, you are refunded automatically and in full.
Is a mailed final demand required before small claims?
Many courts require or strongly expect a written demand first. A Certified demand letter ($12.99) with the amount and a deadline is the standard, and the receipt proves you gave fair notice.
Can I automate past-due letters?
Yes — POST /v1/orders with the letter text and addresses, or wire it through Zapier/n8n/Make webhooks. Each order returns a payment link, or use prepaid credits for hands-off sending.
Are collection letters allowed under your content policy?
Lawful demands for money genuinely owed are explicitly allowed. Impersonating a law firm or collection agency you are not, or threatening action you cannot take, is refused.