Should You Attach Proof of Work to an Invoice?

Should you attach proof of work to an invoice?

Attaching proof of work can be useful when a customer requires evidence that the invoiced service has been completed. This is particularly relevant to project work, maintenance services, repairs, installations, and other jobs where completion may need to be confirmed.

However, not every invoice requires proof of work. The need for supporting evidence depends on the agreement, the type of service, and the customer's requirements.

What counts as proof of completed work?

Proof of work refers to records that help demonstrate which tasks or services were performed. The appropriate evidence depends on the nature of the work and what the customer needs to verify.

For example, a maintenance company might provide a completed service report, while an installation contractor could supply photographs or a signed completion sheet.

• Completed job sheets
• Service reports
• Work completion certificates
• Signed acceptance records
• Before and after photographs
• Inspection reports
• Relevant project completion records

Why might a customer request proof of work?

Customers may request supporting evidence to confirm that the work described on the invoice was completed. This can be particularly useful when the person approving the invoice was not present when the service took place.

Some businesses also require completion records as part of their internal purchasing or payment procedures. Providing the requested evidence can help the customer review the invoice without needing to ask for additional information.

Example of attaching proof of work

Imagine a maintenance business completes a scheduled equipment inspection and sends an invoice for the service. The customer may want confirmation of which equipment was inspected and what work was performed.

The business could attach a completed service report identifying the inspection date, equipment, and relevant findings. The invoice would show the service charge, while the report would provide additional information about the completed work.

Should contractors attach job completion sheets?

Job completion sheets can be useful for contractors who perform individual jobs or site visits. They may record the work carried out, the completion date, the location, and any relevant customer acknowledgement.

When a customer requires a completed job sheet before payment, attaching it to the invoice can make the connection between the work and the charge clearer.

Can photographs be used as proof of work?

Photographs can provide useful supporting evidence for work that can be visually documented. For example, a contractor might provide photographs of a completed installation or a cleaning business might show the finished area.

However, photographs do not always establish that every agreed requirement has been met. They are most useful when combined with clear work descriptions or other relevant completion records.

Should you attach signed completion records?

A signed completion record can help show that a customer or authorised representative acknowledged the work at a particular stage. This may be useful when the agreement requires formal acceptance.

The significance of a signature depends on what the document actually states. A signed attendance sheet, for example, does not necessarily mean that the customer has approved every charge on the invoice.

Does proof of work replace the invoice?

No. Proof of work and an invoice serve different purposes. The invoice identifies the goods or services being charged, the customer, the pricing, and the amount due.

A supporting work record provides additional evidence about the service or project. It does not normally replace the invoice or the payment information the customer needs.

Do you need proof of work for every service invoice?

No. Many service invoices can be issued without separate completion evidence, particularly when the customer already knows that the service was delivered and does not require additional documentation.

Supporting evidence is more useful when the work is difficult to verify, the customer has requested it, or the agreement requires a particular completion record.

Can proof of work help resolve invoice questions?

Relevant completion records can help answer questions about what work was carried out and when it took place. This can be useful if a customer does not recognise a particular service charge or needs more information.

However, proof that work was performed does not automatically establish that every charge was agreed. Clear pricing arrangements and accurate invoice descriptions remain important.

How should proof of work be attached?

Supporting records can be provided as separate files alongside the invoice PDF. Use filenames that identify the invoice or job so the customer can connect the documents.

For example, a file named INV-104-Completion-Report.pdf could accompany invoice INV-104. If several records are included, organise them in a clear order and avoid unnecessary attachments.

What information should a completion report contain?

The information needed depends on the work being performed, but a useful completion report should make it clear which service or job it relates to.

Relevant information may include the job reference, service date, work location, tasks completed, and any required acknowledgement. The report should accurately describe the work rather than making unsupported claims about completion.

Protect customer information in work records

Before sending photographs or completion documents, check whether they contain personal information, confidential project details, or unrelated customer records.

Only provide information that is relevant to the invoice and appropriate for the recipient. This is particularly important when photographs show private premises or documents contain personal details.

Keep proof of work with invoice records

Keeping relevant completion records alongside the corresponding invoice can make it easier to answer questions about previous work. It also helps businesses identify which supporting documents were provided to the customer.

Using consistent invoice numbers, job references, and filenames can help connect the invoice with the relevant completion evidence.

Check completion evidence before sending

Before attaching proof of work, confirm that the document relates to the correct job and customer. Check that dates, descriptions, references, and other details are accurate.

Make sure photographs are relevant and readable, reports are complete, and unnecessary confidential information has been removed. Sending the correct evidence helps customers review the invoice more easily.

Create an invoice for completed work

A clear service invoice should identify the work being billed and show the relevant quantities, rates, and amounts. Supporting completion records can then provide additional evidence where the customer requires it.

InvoiceAtlas lets you add custom invoice items, customer details, quantities, rates, taxes, discounts, and notes before downloading your completed invoice as a PDF for free. You can then send any relevant proof of work alongside the invoice.