PO, AP Contact, Billing Entity, Net Terms: A SaaS Guide

Your SaaS invoice for 24,000 dollars went out on the first of the month. It's day 40 and nothing has moved. You call. The buyer's accounts payable team says it was never entered because it had no PO number, the billing name doesn't match their registered entity, and the reminder went to the sales champion who stopped reading finance email weeks ago. None of that is a dispute about the money. It's four fields nobody agreed on up front.

Here are the four terms that cause most of those stalls, defined plainly, then shown on one invoice.

PO number: the buyer's permission slip

A purchase order (PO) number is a reference the buyer's own system generates before they commit to spending. Their procurement team approves the purchase, the system issues a number, and from that point the buyer's accounts payable will only pay invoices that carry it. No number, no match, no payment. The invoice sits in a queue until someone notices.

For small buyers this rarely matters. For mid-market and enterprise SaaS deals it is often mandatory, and the format is strict: something like PO-2024-00817, not a word or a name. If you want the full background on how these work, the guide to purchase orders covers it. The practical rule: get the PO number before you issue the invoice, or build a way for the buyer to add it after.

That last part is where most tools fail you. A PDF is frozen. The buyer emails you the number, you edit the file, you resend, they reconcile the versions. On JupiterInvoice the recipient can add the PO number themselves on the invoice you already sent. You get notified, and it's logged as a tracked amendment, not a brand-new version.

AP contact: who actually pays

The AP contact is the person or shared mailbox in accounts payable who processes and pays invoices. This is almost never the person who signed the contract. Your sales champion wanted the product. The AP clerk pays for it. Those are different jobs, usually different departments, and sometimes different buildings.

Send a 24,000 dollar invoice only to your champion and it can sit in their inbox for three weeks while they mean to forward it. You need the invoice in front of AP directly. In JupiterInvoice the recipient can set an AP contact and forward the invoice to the right inbox without you chasing anyone for an email address. If you are stuck on this today, getting your invoice to accounts payable walks through the handoff.

Billing entity: the legal name on the money

The billing entity is the exact legal name and address that the invoice must be addressed to. A buyer you know as "Northwind" might pay as "Northwind Technologies LLC" from a specific registered address, with a tax ID attached. If your invoice says "Northwind" or uses the office you've been emailing, AP may reject it or hold it for correction.

This bites SaaS sellers in particular because the signup email, the champion's business card, and the paying legal entity are often three different things. The buyer knows their correct billing details; you are guessing. So let them fill it in. JupiterInvoice lets the recipient update the billing entity and billing address directly, and if they get it wrong, you can revert it in one click. For why the mismatch happens so often, see fixing wrong billing details on a sent invoice.

Net terms: when the clock says you get paid

Net terms state how many days the buyer has to pay after the invoice date. Net 30 means 30 days. Net 60 means 60. "Due on receipt" means now, in theory. The number is a promise about timing, and on larger SaaS contracts the buyer's standard terms often override whatever you wrote.

Two things trip people up. First, the clock usually starts at the invoice date, not the day the buyer finally enters it into their system, which is why a late-entered invoice quietly pays late. Second, agreeing to Net 60 on an annual contract means you wait two months for 24,000 dollars, every renewal. Pick the number deliberately. Net 15 vs Net 30 vs Net 60 breaks down the trade-off, and the due date calculator turns your terms into an actual date.

The four fields on one invoice

Put together, a clean B2B SaaS invoice for an annual seat renewal looks like this:

The split matters. The buyer owns the facts only they know: their legal name, their PO number, where AP sits. You own the commercial facts: what you charged, in what currency, due when. The buyer can't change your pricing or terms without asking in the comment thread, so your numbers stay yours while their details stay accurate. That division is the whole point of invoicing built for the parts Stripe Billing won't do, where PO numbers, AP routing, and buyer-side billing details actually have a home.

Agree on these four terms before the first invoice of a contract goes out, not after it stalls. When you're ready, create the invoice and let the buyer fill in their half.