Vendor Setup at Big Brands: Supplier Portals, Onboarding Forms, and Why Your First Invoice Stalls

You signed with a bigger brand than usual. The stream went well, you sent the invoice the same night, and the payment terms were net-30. Day 30 comes and goes. When you chase, the reply is something like: "We can't find you in our system — have you completed vendor onboarding?"

Nobody mentioned vendor onboarding.

This is often why a first payment from a large company runs late, and it has little to do with whether the brand liked your work. Larger companies pay through an accounts-payable (AP) process built for suppliers of every kind, and a creator is one more supplier. Until you exist in that system, your invoice usually has nowhere to go.

This post covers what vendor setup usually involves, what a supplier portal is (using Coupa's own documentation as the worked example), how purchase orders affect your invoice, and a checklist to send at signing so the first payment doesn't stall.

Who's actually paying you

At a small brand, the person who emailed you might also be the person who pays you. At a large one, they're usually not. Your contact is in marketing. They can approve the deal, but the payment goes out from finance, often on a fixed payment run, to suppliers who are already set up as vendors.

That means two separate approvals have to happen:

1. Marketing approves the deal, which you already have.
2. AP approves you as a vendor, which you might not have yet.

Your contact may not know step 2 exists until your invoice bounces off it. Asking about it at signing is the single most useful thing on this page.

What vendor setup usually asks for

It varies by company, but the same handful of items come up again and again:

• A tax form. A W-9 if you're a US person, a W-8BEN if you're a foreign individual. The W-9 vs W-8BEN post covers which one you need and what a missing one can cost you. Send it through the vendor portal or another secure channel, not as a plain email attachment.
• Banking details for the payment method they use, often with something that proves the account is yours. Coupa, for example, says a customer "may require that you upload supporting documents to verify the account during onboarding," and that when you add a bank account during first-time onboarding, "you must upload at least one supporting document to proceed in the onboarding process."¹
• Your legal name and address, matching your tax form. If your invoice says your channel name and your tax form says your legal name, someone in AP has to reconcile the two before paying.
• A remit-to address or payment location: where payments and remittance notices should go.
• Sometimes, a supplier agreement or questionnaire. Large companies sometimes ask every vendor to accept standard supplier terms or answer a short compliance form. Read it like you'd read any contract. If it conflicts with your sponsorship agreement, ask which one governs.

None of this is unusual or a sign of a bad brand. It is a sign the payment will take longer than the contract suggests if you wait to be asked.

Supplier portals: what they are

Many large companies run their purchasing and AP through a procurement platform, and suppliers interact with it through a supplier portal. Coupa is one widely used example, and it publishes its supplier documentation openly, so it's the one quoted here. Other platforms work differently, and the customer's own configuration matters more than the platform. Treat the details below as an example, not a rule.

It's free to you. Coupa: "Coupa doesn't charge suppliers to use the CSP" (the Coupa Supplier Portal).² If any portal asks you to pay to be set up as a vendor for a sponsorship, stop and confirm with your brand contact through a channel you already trust.

You usually join by invitation. Coupa says you can "ask your customer to send you an invitation email," and that if you register yourself instead, you should "use the same email address to register that your customer used to invite you."² In practice: when the brand's AP team invites you, register with exactly that email. A second account under a different email is a common way to end up invisible to the customer.

What happens inside it depends on the customer. Coupa's overview is careful about this: suppliers can manage things "depending on the customer's specific Coupa configuration," including purchase orders, invoices, and "checking the status of transactions."³ Its first-time guide says completing onboarding "creates your basic business profile details, including legal entity and payment methods, required for most processes."⁴

Not every customer uses the portal for invoices. Coupa lists several invoicing methods a customer might choose, including the portal itself, an emailed spreadsheet, and "Supplier Actionable Notifications (SAN), where you act on an email without creating an account."⁵ So the first question is not "how do I use the portal?" but "how do you want me to invoice?"

The portal doesn't decide when you're paid. Once an invoice is approved, Coupa says you need to do "nothing" more: "The invoice is your customer's queue and you'll be paid based on the payment terms you set with your customer."⁵ And for questions about an unpaid invoice, "contact your customer directly."⁵ The portal is plumbing; your contract still sets the terms.

Purchase orders: the number your invoice needs

A purchase order (PO) is the brand's internal record that it has agreed to buy something from you, for a set amount. Many AP teams match each invoice against a PO before paying it. If your invoice doesn't reference the right PO, it can't be matched, and it waits.

Two things from Coupa's documentation are worth knowing even if your brand uses something else:

• Whether you need a PO at all is the customer's call. Asked whether a supplier needs a PO before invoicing, Coupa's answer is: "It depends on how your customer has you set up. Contact them and ask how you're configured, and if you can send non-PO backed invoices."⁵
• Emailing a PDF can be slower. Coupa says emailing a PDF invoice directly to the customer "is ideal for invoices without a PO," but "your customer might have to manually enter the PDF invoice information into Coupa, which may cause a delay in payment."⁵

Two more that matter once you're set up:

• You can't edit an invoice after you submit it. "Once an invoice is submitted, it can't be changed in any way."⁵ Fixing a mistake means a credit note and a new invoice, or asking the customer to dispute or void the original. Check the PO number, amount, and dates before you submit.
• You can't change a PO's price yourself. "You cannot change a price on a PO through the CSP. If you need a change order on a PO, talk to your customer about their policies."⁶ If the deal grew (say an extra deliverable), get the PO updated before you invoice the larger amount, or the invoice won't match.

For a multi-month deal, ask whether they'll raise one PO for the whole term and let you invoice against it in parts. Coupa supports this pattern: "You can invoice multiple times against a single PO."⁶

Why the first invoice is the slow one

Put the pieces together and the usual first-payment failure looks like this:

1. You invoice on time, by email, to your marketing contact.
2. They forward it to AP. AP can't pay you, because you're not set up as a vendor, there's no PO, or both.
3. Nobody tells you. The invoice sits.
4. You chase at day 30. Someone sends an onboarding invite.
5. You complete onboarding, AP raises a PO, and you're told to resubmit the invoice against it.
6. AP clocks your net-30 from the resubmitted invoice, not the original, unless you ask them to honour the original invoice date (your terms run from the invoice date, not from when they set you up). Either way, the payment lands in whatever run comes next.

Every step here is ordinary. The delay comes from doing them in sequence, after the invoice, instead of in parallel with the deal. The second invoice from the same brand is usually much faster, because steps 2 through 5 are already done.

This is one of the patterns behind why creators get paid late, and it's the first thing to rule out before you escalate a sponsor that's paying late.

The checklist: send this at signing

Send something like this to your brand contact the day the contract is signed, not the day you invoice:

Thanks, looking forward to it. So the invoice doesn't get stuck on our side, could you check with your AP team on a few things?

1. Do I need to be set up as a vendor first? If so, can they send the onboarding invite to [email]?
2. Which tax form do you need from me (W-9 or W-8BEN)?
3. Will there be a PO number I should put on the invoice? If so, when will it be issued?
4. How should I submit the invoice: through a supplier portal, by email, or another way? And to whom?
5. Is there a payment run schedule I should know about?

Happy to get all of this done before the stream so payment isn't held up.

Then, on your side:

• Register with the exact email the invite went to, and finish onboarding the same day.
• Use one legal name everywhere: tax form, invoice, bank account. The invoice template has a line for it.
• Put the PO number on the invoice if there is one, and check that the amount matches the PO before you submit.
• Log what you sent and when: form sent, onboarding done, PO received, invoice submitted. If you need to chase later, the chase email templates work much better when you can say exactly which step is complete.
• Don't send bank details or tax IDs to an address you can't verify. If an "onboarding" request arrives from an unfamiliar domain, confirm it with your brand contact first.

For which payment rails cost you least once you are set up, see how brands pay creators.

FAQ

Why hasn't a big brand paid my first invoice?
Often because you aren't set up as a vendor in their accounts-payable system yet, or your invoice doesn't reference a purchase order they can match it to. Ask your contact whether vendor onboarding is complete and whether a PO has been issued before you escalate.

What is a supplier portal?
It's the website a company's procurement platform gives its suppliers for onboarding, purchase orders, and invoices. Coupa's, for example, is the Coupa Supplier Portal. Coupa says it doesn't charge suppliers to use it, and that what you can do in it depends on how each customer has configured it.

Do I need a PO number to invoice a brand?
It depends on the brand. Coupa's own guidance is to ask your customer how you're set up and whether you can send invoices that aren't backed by a PO. If they issue one, put it on your invoice and make sure the amounts match.

Can I fix an invoice after I submit it in a supplier portal?
In Coupa, no. Once an invoice is submitted it can't be changed. You'd issue a credit note and a new invoice, or ask the customer to dispute or void the original. Check the PO number and amount before you submit.

Should I pay to be set up as a vendor?
Coupa says it doesn't charge suppliers to use its supplier portal. If a vendor-setup request asks you for money, confirm it with your brand contact through a channel you already trust before doing anything.