Business admin for UK trades
Customer PO Numbers and Invoice References: A Trade Admin Checklist
When a letting agent, builder or another business orders work, their accounts team may use a purchase-order number or another reference to match the invoice. Ask what they need early and keep it with the job. This is a workflow checklist, not a statement that every customer must issue a PO.
Distinguish the references
Your job reference identifies the work inside your business. A customer purchase-order reference identifies their order or internal approval. An invoice number identifies the invoice. A property or site reference can identify where the work took place. They can be related without being interchangeable.
Record each in a named field rather than placing several numbers into an unexplained note. Where there are several properties or instructions, check which reference belongs to this job. Do not reuse a previous order number simply because the organisation is the same.
Ask the ordering contact about the billing process
- Does this customer require an order or other reference for this work?
- Who supplies it, and where will it be confirmed?
- Which organisation and contact should receive the invoice?
- Is there an agreed email address or submission portal?
- Which completion records or job references should accompany it?
- Who resolves a missing or conflicting instruction?
Record the instructions actually provided. A particular customer’s submission process is not a universal UK invoicing rule. This checklist does not replace accounting advice or the requirements that apply to your invoice.
Treat a missing reference as an owned task
If a reference is needed but unavailable, name the person who will obtain it and the point at which they will check again. Keep the job’s work position separate from its invoice-readiness position. “Visit completed” does not say whether the office has the billing details.
Where instructions conflict, ask the customer’s appropriate contact to clarify. Do not invent a PO, substitute another job’s number or alter a document to make it appear approved. Escalate to the business owner where the missing information affects a commitment or the agreed process.
An invoice-handover example
The office sees the blocker and the next action without searching a customer’s entire message history. This does not imply a particular customer can legally withhold payment or that a PO determines contractual rights.
Check your current invoice and job fields
Look for a customer reference field and a way to carry the right job information into invoice preparation. Check the current product documentation and the actual document preview. An internal note is not necessarily visible on the customer’s invoice.
Test with a clearly fictional draft: does the chosen reference appear where the customer expects it, and does the office retain the link back to the job? Do not automatically create a customer order from a supplier purchase order; buying your materials and receiving your customer’s instruction are different events.
Download the billing-reference checklist
Download the invoice-handover worksheet (CSV). Use it for business customers whose processes need these details. If existing job and accounting software already stores them reliably, put the checklist there rather than maintaining a separate spreadsheet.
Review the reasons invoices return for correction. A wrong address, absent customer reference and disputed work are different problems and need different responses. Correcting the handover can help with the first two; it does not resolve a disagreement about the work.
Sources and review
Reviewed 24 October 2026. Xero: check current invoice editing and reference fields.
Source material supports the specific examples referenced. The checklists, worksheets and illustrative scenarios are MMD's suggested business-admin processes, not customer results. Product workflows can change; check current documentation for the software you use.