The first invoice is where you find out how your client pays vendors. And if you find out by sending the invoice and waiting, you’re going to wait a long time.
The scenario plays out every time: you complete Week 1 or send the first deliverable. You send an invoice. Two weeks pass. You send a polite follow-up. The client apologizes and explains that the invoice went to the wrong email, or it needed a PO number, or their AP system requires you to be a registered vendor, or their CFO is the only one who approves payments and he was traveling.
None of this is malicious. All of it was completely predictable, if you’d asked.
Five questions. Four minutes. During the kickoff call, before any work begins. The billing setup conversation is the most underrated part of client onboarding, and skipping it costs freelancers thousands of dollars a year in delayed cash flow.
Why Billing Conversations Feel Awkward and Why You Have to Have Them Anyway
Freelancers avoid billing conversations during kickoff because they don’t want to seem transactional when they’re trying to build rapport. The client just signed. Everyone is excited. Asking about accounts payable feels like jumping from the wedding to the prenup.
But this is exactly the right time to have this conversation. The client is engaged, the relationship is fresh, and billing details are administrative, not negotiating. You’re not talking about whether you’ll get paid. You’re asking how to make sure the machinery works. Most clients appreciate the professionalism.
The way to set it up: “Before we move to the project plan, I want to cover billing setup so your first invoice arrives correctly and gets processed without any back and forth. Four or five quick questions, do you have 3 minutes?”
Nobody says no to that framing.
The 5 Questions
Question 1: “What email address should I send invoices to?”
Never assume. Never use the email address you’ve been communicating with unless you’ve confirmed it’s also the billing email. In most companies, and any company that’s more than a 10-person startup, there’s a separate email for accounts payable. Common formats: billing@, ap@, invoices@, accounting@.
Get the exact email and add it to your project admin folder. When you send invoices, CC your project contact and send directly to the billing email.
Why it matters: An invoice sent to your contact’s inbox may sit there for days if they’re busy, out of office, or don’t think of themselves as the payment processor. AP addresses route directly to the person whose job is to process payments.
Question 2: “Is there a separate accounts payable contact I should know?”
Sometimes the billing email is monitored by a specific person, an AP manager, a bookkeeper, or an executive assistant who handles vendor payments. Knowing their name and having a backup contact is valuable when invoices go unanswered.
“In case I need to follow up on an invoice, is there someone in accounts payable I should reach out to?” Most clients give you a name without any hesitation.
This question also tells you how formal the client’s payment process is. If they don’t have an AP contact, you’re probably dealing with a small company where the owner approves payments personally, different process, different follow-up approach.
Question 3: “Do you require a purchase order number for vendor invoices?”
This is the one that surprises freelancers most. Many mid-size and large companies require a PO number on every invoice before payment can be processed. If your invoice arrives without a PO number, it doesn’t get paid, it gets held until someone creates a PO, which can take days to weeks depending on how busy procurement is.
The answer is almost always: yes or no. If yes, ask: “How do I get a PO number generated for this project?” Walk through whatever process they have, get the number before you send your first invoice, and include it on the invoice under a “PO Number:” field.
Some companies also require you to reference the PO on the invoice subject line. Ask: “Any specific format you need on the invoice?”
A missing PO number on an invoice isn’t a payment problem, it’s an administrative hold. The client isn’t deciding not to pay you. Their system is literally unable to process the payment. Get the PO number before you send the invoice and the hold never happens.
Question 4: “Do I need to register in a vendor or payment portal?”
Enterprise companies, government entities, and many large corporations require vendors to be registered in their vendor management system before a payment can be processed. Ariba, Coupa, SAP, and similar platforms are common examples.
If the answer is yes, you need to be registered before you send your first invoice, not after. Vendor registration typically takes 1-5 business days. Get the registration process started in Week 1.
Ask: “Is there anything I need to register or sign up for to receive payments? I want to make sure I’m set up in your system before the first invoice.”
If the client isn’t sure, ask for an intro to their procurement or AP team, they’ll know immediately.
Question 5: “What payment method do you prefer, and what do I need to send you to use it?”
ACH (bank transfer), wire, check, and payment platforms (Bill.com, Tipalti, Stripe) all require different information from you. Find out which method they use and provide whatever they need right now:
- ACH/wire: Routing number and account number
- Check: Mailing address
- Bill.com: Email address for the invoice request
- Stripe/PayPal: Link for payment or email
Provide your payment details in the same kickoff conversation rather than waiting for them to ask. This eliminates one more round of back-and-forth before the first payment.
The Billing Setup Email
After the kickoff call, send a billing setup confirmation email within 24 hours. This is both a record and a proactive step:
Subject: Billing Setup Confirmed, [Project Name]
Hi [Name],
Following our kickoff call, here’s the billing information for the record:
Invoice recipient: billing@[company].com (CC: [contact name]) AP Contact: [Name], [title] PO Requirement: [PO #XXXXX, included on all invoices / Not required] Payment Portal: [Registered / Not required] Payment Method: ACH, my banking details below
[Routing: XXXXXXXXX / Account: XXXXXXXXX]
Payment terms are Net 15 per our contract. My first invoice will be sent on [date] for [amount / first milestone / per retainer schedule].
Let me know if anything needs updating.
[Your name]
This email serves three purposes. It confirms the setup details. It establishes the payment terms in writing a second time. And it tells them exactly when to expect the first invoice, which mentally prepares both the client and their AP team.
What to Do When Billing Setup Gets Complicated
Some enterprise clients have genuinely complex vendor onboarding requirements. Supplier diversity certifications, insurance certificates, W-9s, bank verification letters, vendor registration forms with 30 fields.
Don’t fight it. Start the process in Week 1. Ask for the registration forms, complete them immediately, and follow up within 5 business days if you haven’t received confirmation.
Add a clause to your contract that says billing timelines (payment within Net 15) begin when vendor registration is complete, not when work begins. This protects your cash flow if their vendor process is slower than expected.
For registration processes that are expected to take more than 2 weeks, request an expedited process or an interim payment mechanism (corporate card, PayPal) for the first invoice while registration is underway. Most clients will accommodate this if you ask directly and explain the reason.
The bottom line: billing setup friction at a large company is not a red flag, it’s bureaucracy. Navigate it methodically in Week 1 and your cash flow stays clean.
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