Invoice rejected for a missing purchase order? A consultant’s guide to getting paid

Find out whether the invoice is rejected, disputed or waiting for approval

Do not start by sending the same invoice again. Ask accounts payable to confirm its exact status and the action needed to move it forward. Request the rejection message or portal status so you are responding to the actual problem rather than a forwarded summary.

Use the distinctions below as questions, not assumptions about the client’s system. In particular, ask whether anyone disputes the scope, delivery or amount. If the problem is only a missing reference, keep that administrative correction separate from any discussion about the quality or price of your work.

Finish the exchange by asking for a named owner of the next action. “Waiting for approval” is not yet a resolution plan: ask whose approval is outstanding and who can follow up with them.

• Rejected or returned: was the invoice excluded from processing, and what must change before it can be accepted?
• Waiting for approval: has the invoice been received, and who needs to confirm the work or authorise payment?
• Disputed: which deliverable, fee or contractual requirement is being questioned?

Check what your contract says about purchase orders and payment terms

Gather the signed agreement, accepted proposal, statement of work, relevant client terms and commissioning emails. Look for references to purchase orders, valid invoices, acceptance of deliverables and the event that starts the payment period. Note any uncertainty about which terms were agreed rather than trying to resolve it from memory.

Treat procurement instructions and contractual payment wording as separate checks. For example, Swansea Council says invoices must show the relevant PO number on the invoice itself, not merely in the email, and that processing cannot continue until a compliant invoice is received. Peterborough City Council instructs suppliers to obtain a PO before providing services. These are specific buyers’ published requirements, not evidence that every consultancy invoice follows the same rules.

Do not assume either that an internal policy automatically changes your agreement or that it can safely be ignored. If the client proposes restarting the payment period, ask which agreed term supports that position. The supplied guidance does not establish the legal outcome for your contract; check GOV.UK or seek a professional adviser’s view if the wording or payment entitlement is disputed.

Ask your client sponsor and accounts payable for a clear resolution

Contact the person who commissioned your work alongside accounts payable. Ask your sponsor to confirm the agreed scope, fee and delivery, and to identify whoever can issue the PO or authorise the appropriate exception. Ask accounts payable to specify what it needs to accept and process the invoice.

Keep the request factual and easy to forward. Include the invoice reference, project name, amount and original submission date using your actual records. Attach the relevant acceptance or commissioning evidence, rather than an entire project email archive.

Suggested wording: “Accounts payable has advised that this invoice is blocked because a PO reference is missing. Please confirm who can arrange the required purchasing approval and whether any part of the work or fee is disputed. I have attached the agreed scope and delivery evidence. Please also confirm the correction needed, who owns the next action and the expected payment date.”

Resubmit with the evidence and references the client needs

Once you have the reference, check it against the client’s instructions and the work being invoiced. Ask the sponsor to resolve any mismatch in scope or value before resubmitting. Follow the specified submission route: Swansea’s guidance, for example, requires PDF invoices with one invoice per document. Do not assume that another client wants the same format.

Make the relationship between the original submission and the corrected document explicit. Ask accounts payable how to submit the correction against the existing record rather than creating an unintended duplicate. Keep a copy of the original invoice, rejection, corrected version and submission acknowledgement.

Do not change the invoice date or accept a revised due date simply to clear the query without understanding the reason. You could write: “Attached is the invoice corrected to include the requested PO reference, relating to the original submission on [date]. Please confirm receipt and payment on the original due date of [date]. If you consider a different date applies, please explain the basis in our agreed terms.” This records your position; it does not guarantee the contractual outcome.

• Agreed scope and fee: the accepted proposal, statement of work or relevant commissioning correspondence.
• Delivery evidence: the report handover, workshop completion message or milestone approval.
• Processing details: the confirmed PO reference, correct customer details and required submission route.
• Payment history: the original submission evidence and correspondence about the rejection.

Confirm the payment date and escalate if the invoice remains unpaid

After resubmission, ask for confirmation that the invoice has been received, that the PO issue is resolved and that no further approval is outstanding. Then ask for the expected payment date. If the answer is “the next payment run”, request the actual date and confirmation that your invoice is included.

If the date passes or no owner responds, escalate with a concise chronology: commissioning, delivery, original invoice submission, rejection, correction and subsequent promises. Ask your sponsor to involve the relevant procurement or finance lead. Keep the request focused on the outstanding decision and the person authorised to make it.

For your own cash planning, distinguish a requested payment date from one the client has confirmed. If the matter becomes a contractual dispute or remains unresolved, check current GOV.UK guidance and speak to a professional adviser before making claims about interest, recovery charges or legal action. Do not assume that a missing PO settles either party’s legal position.

Add a purchase-order check before starting your next project

Include purchasing questions in your project setup, alongside scope, fee and delivery dates. Ask whether a PO is required before work begins, who raises it and what information they need from you. Peterborough’s published instructions explicitly require suppliers to have a PO before providing services, illustrating why this check belongs before delivery rather than at invoicing.

For phased consultancy work, ask whether the reference covers the full engagement or only the current stage. Before accepting additional workshops, analysis or advisory time, confirm whether the purchasing approval needs updating. Keep that question alongside your agreement on the extra work and fee.

Agree the invoice recipient, submission route and delivery approver while your sponsor is actively setting up the project. If a required PO has not arrived, ask for the approved route forward and consider delaying the start rather than relying on an informal promise to sort it out later.

• Is a PO required, and must it be issued before work starts?
• Who is responsible for arranging it?
• Does it cover the agreed scope and fee?
• Who confirms completion or approves each milestone?
• Where should invoices go, and which references must appear?
• What do the agreed terms say about when payment becomes due?

How Invoices and payments helps

HappyNoodle’s invoices and payments workflow lets you create invoices from the work, make payment simple and keep polite reminders connected to the right client. For a missing-PO problem, use that workflow alongside the checks above: establish what the client needs, resolve the reference query with your sponsor and confirm the expected payment date. Keep reminder wording focused on the outstanding action rather than repeating a generic demand. The purchasing approval and any disagreement over payment terms still need direct attention from you and the client.