The purchase order problem: how to get paid faster by big companies

You did the work. You sent the invoice. Thirty days passed. You chased. The reply: “Sorry, we need a purchase order number on the invoice before we can process this. Can you resend?”

That’s four to six weeks of delay for a process that takes the client’s procurement team two to three days once they get involved. None of it was necessary.

Why big companies can’t pay without a PO

A purchase order is an internal document that authorises a payment. When a company creates one, they assign it a number. That number has to appear on your invoice for their accounting system to match it to an approved spend and process payment.

Large organisations use PO systems to track spending, enforce budget approvals, and reconcile accounts. If your invoice arrives without a PO number, the accounting system can’t match it — and it either gets held pending manual review or bounced back entirely.

The critical point: the PO has to exist before you invoice. You can’t add a PO number to an invoice after the fact without resending it. And resending resets the clock on their payment terms.

The one question to ask

At the start of every engagement with a company that has a finance department, ask this:

“Do you need a purchase order number on my invoice?”

Ask it in the same conversation where you discuss the project start date and payment terms. Before you start work.

If the answer is yes: get the number before you do anything else. If they don’t have one yet, that means their internal approval process hasn’t cleared the spend. Find out when it will. Starting work without a PO when one is required means your invoice will wait — not the two weeks in your payment terms, but two weeks plus however long procurement takes to generate the PO retroactively.

If the answer is no: one question, thirty seconds, potentially three to four weeks saved.

What to do if you’ve already started

You’ve been working for two weeks and forgot to ask. Don’t wait until you invoice.

Go to your contact now: “Quick admin question — do you need a PO number on the invoice?” If yes, give them a few days to sort it before you send. That’s still much better than discovering the problem after.

What you don’t want is to send the invoice, wait 30 days, chase, get told about the PO requirement, resend, and restart the payment clock. That turns a 30-day payment cycle into 60 or 75.

Other friction points with corporate clients

Purchase orders are the most common blocker, but not the only one.

Supplier registration. Some large companies require you to register as a vendor in their procurement system before they can pay you at all. This can take a week or two. Ask early: “Is there a supplier registration process I need to complete?”

AP contact vs. your day-to-day contact. The person you worked with usually has limited power over accounts payable. When following up on an invoice, ask for the AP email address and cc them directly. Your project contact can’t approve payment — they can only chase internally.

Payment run schedules. Large companies don’t process invoices daily. AP runs happen weekly, fortnightly, sometimes monthly. An invoice that arrives the day after a run can wait 30 days just to enter the processing queue. Ask when the next run is before you send.

Payment terms. Net 60 and Net 90 are standard at many large companies. If that’s unacceptable, negotiate before you start — not after you’ve invoiced.

When the invoice is already stuck

If the problem is a missing PO, ask your contact to expedite the PO generation through their procurement team. Give them the invoice number and amount precisely. Don’t ask “can you chase the payment” — ask “can you get me the PO number so I can resend today?”

Once you have the number, resend immediately. Reference the original invoice number, mark it as a revised version, and put the PO number prominently at the top. Then follow up directly with AP — not just your contact.

The full escalation sequence for overdue invoices applies here too, but the cause is almost always process, not intent. Identify the actual blocker before escalating.

The documentation problem

When a corporate client finally processes payment — sometimes months after delivery — they’ll occasionally request backup documentation to validate the invoice amount. This is where having a clean billing record saves time.

A complete invoice with specific line items is your first line of defence. But if you bill hourly, having a clear log of hours by date and client makes disputes much shorter.

Timescanner generates a billing report directly from your calendar events — hours by client, period, and date — so if an invoice gets queried six weeks after delivery, the record is already there. Works with any iCal-compatible calendar: Google Calendar, Outlook, iCloud, Proton Calendar, and others.