When a Client Insists You Use Their Vendor Portal

A new client sends the purchase order, then adds a line you have seen before: "Please register in our vendor portal to get paid." Now you are filling out a supplier onboarding form, uploading a W-9, picking a password you will never use again, and waiting on an approval email that may take a week. All to send one invoice for work you already finished.

Sometimes the portal is mandatory and you have no choice. Often it is not. The request is a proxy for a handful of concrete things the client's accounts payable team needs, and you can supply every one of them without an account on someone else's system.

What the portal is actually asking for

Strip away the login screen and a vendor portal collects four things from you and gives the client one thing in return.

• A verified billing entity and remittance address, so payment lands in the right place.
• Tax identity: a W-9 or W-8BEN, an EIN or VAT number, so they can report and withhold correctly.
• An invoice tied to a PO number, because their AP team will not pay a bill it cannot match to an approved order.
• A named contact and an audit trail of who approved what and when.

The portal exists to route your invoice to the right approver and record the decision. That is a real need. What is not real is the assumption that the only way to meet it is a supplier account you maintain for one project. If you want the longer version of how to respond when this comes up, we wrote a full walkthrough on what to do when a client wants you in their portal.

What the portal actually costs you

Portals are built for the buyer, not for you. The registration alone can eat an hour. Then the portal formats your invoice its own way, hides the approval status, and often has no field for your bank details or your own invoice number. You lose your invoice numbering sequence, which matters when your bookkeeper reconciles the year.

Worse, you lose visibility. Your invoice sits in a queue somewhere and you have no idea whether it was opened, approved, or bounced back for a missing field. A net 30 invoice quietly becomes a 55 day one because nobody told you the billing entity was wrong until you chased. If AP keeps sending things back, the reasons are usually the same handful, which we broke down in the AP approval checklist your invoice must pass.

How a shared invoice link covers the same ground

A collaborative invoice link does the routing and approval work a portal does, but the recipient never signs up for anything. You create the invoice, generate a private link, and send it. The client opens it and works with it directly.

The parts AP cares about are all editable on the recipient's side. They can add the PO number themselves, correct the billing entity and billing address, and set the accounts payable contact. You get notified of each change and can revert it in one click if something looks off. Because those are tracked amendments rather than rewrites, your invoice number and issue date stay locked. If the client needs a real change to pricing, terms, or line items, they request it and you approve or decline, which creates a clean version history instead of a mystery.

The approval step is the piece that replaces the portal. The recipient can forward the invoice straight to their AP team, and whoever holds the budget approves it. Once a version is approved, it locks permanently, so there is a fixed record of exactly what was agreed. That is the audit trail the portal was trying to build, minus the onboarding. You can see how that plays out in practice in the flow where a recipient approves without an account.

When you need the PO number added after the fact

A common portal trigger is the PO arriving late. You already sent the invoice, then procurement issues the number. With a link, the client just types it into the PO field on the live invoice. No reissue, no new PDF, no portal round trip. The mechanics are covered in our note on adding a PO number after sending, and if you are not sure what format their system expects, the PO number format checker will flag an obvious mismatch before it stalls in AP.

How to propose the link instead

The move is not to refuse the portal. It is to offer an equivalent that costs the client nothing and gets them paid on time. Try something like: "Happy to get you what you need. Instead of onboarding, here is a link to the invoice where your team can add the PO number, set the AP contact, and approve it directly. You will have a locked record once it is signed off."

Most AP teams accept this because it hands them what they actually want: a matched PO, a named approver, and a permanent record. The ones that cannot are usually bound by a procurement rule, and then you register. But you will have saved the trip on every client who only asked because the portal is their default.

To set one up, create the invoice with your full payment details, share the link, and let the client fill in their side. Agencies dealing with procurement-heavy clients will find more of this in getting an agency invoice through client procurement. If you would rather send an invoice as a link than an attachment on every job, that is the default here, not a workaround.