What is proof of work: proof of work explained in the field service sense

Search proof of work and most results describe the blockchain consensus mechanism, where computers expend energy solving puzzles to validate transactions. That is a different subject entirely. In field service, facilities and contracting, proof of work means documented visual evidence that a job was actually completed to standard, captured at the point of completion, so that a supervisor, customer or auditor can look at the work rather than take somebody's word for it.

The rest of this entry is about that second meaning. You will also see it written as completion evidence, job completion documentation, or visual proof of work.

What does proof of work mean in practice?

A status field saying Completed tells you that somebody marked the job complete. It does not show you the work.

That is the whole gap. Between the moment a technician or contractor leaves site and the moment anyone else forms a view about what happened there, the only record is usually a tick box and a signature. Proof of work closes that gap with evidence that stands on its own:

• The completed work itself, shown clearly enough to assess.
• Before and after, so the change is visible rather than asserted.
• The surrounding area, showing the site was left safe and clean.
• Serial numbers or part identifiers for anything replaced.
• A spoken or written explanation of what was done and why.

Proof of work: a worked example

A contractor replaces a failed pump in a plant room. Completion capture requires the old unit before removal, the new unit installed with its rating plate legible, the pipework connections, the pressure reading under load, and the plant room left clear. Six months later, when a leak is blamed on that install, the supervisor can look at the connections as they were on the day rather than reconstructing the job from memory.

How is proof of work captured and verified?

Capture and verification are two separate problems, and teams usually solve only the first.

Capture is about specifying what must be shown before a job can be closed. Asking for a few photos when you are finished produces inconsistent, unusable evidence. A defined sequence produces something comparable across jobs, sites and contractors.

Verification is about what you know regarding the file itself. Reasonable questions to ask of any completion evidence:

• Was this recorded during the job, or selected from a camera roll afterwards?
• When did our organisation receive it?
• Is the file we are looking at today identical to the one originally received?
• What happened to the case after it arrived?

Cryptographic hashing answers the third question, and a recorded receipt time answers the second. Be precise about the last one, because it is routinely overstated: a server timestamp proves when a submission was received, not when the work was performed. That distinction is what makes the timestamp useful without claiming more than it can support.

Why proof of work matters commercially

Rework and disputes are where the value sits, and the numbers are worth quoting carefully.

Research by Peter E. D. Love, published in the Journal of Construction Engineering and Management and covered by the American Society of Civil Engineers, measured precompletion rework at 0.38 percent of contract value, rising to 0.76 percent once postcompletion corrections were included, against earlier literature estimates running as high as 12.4 percent. The same study found actual rework costs were underreported by 300 percent because the data simply were not available (ASCE Civil Engineering Source).

The UK Get It Right Initiative puts the direct cost of avoidable error in the order of 5 percent of project value, with total error costs estimated at 10 to 25 percent of project cost, and its own research pointing closer to 21 percent (getitright.uk.com).

The gap between those two sets of figures is the point. Nobody agrees on the size of the rework problem, largely because the evidence of what was actually done is missing. That is an argument for better completion records, not for picking whichever percentage suits the business case.

Where proof of work gets used

• Contractor accountability, where the contracting organisation was never on site.
• Remote quality assurance, reviewing completed work before deciding whether physical verification is needed.
• Dispute handling, months or years after the fact.
• Warranty and audit, where the record has to outlive the people who created it.
• Handovers between shifts, departments or organisations.

Mistakes worth avoiding

Collecting evidence nobody reviews. A folder of completion photos that is only opened during a dispute is a filing habit, not a quality process.

Leaving the shot list to the technician. Without a defined sequence, one person sends twelve images and the next sends two.

Treating evidence as proof of everything. A genuine recording can still show an incomplete or misleading picture. Visual evidence makes the record more structured and more verifiable. It does not settle every question by itself.

Storing it away from the case. Evidence separated from the job it belongs to loses most of its value.

More on this in proof of work in field service and equipment verification.

If you want the process rather than the folder, Venta Capture, a product of VentaVid, builds completion capture into a guided flow: the person on site is walked through the required views and questions, and the submission arrives as a structured case with transcript, receipt timestamp and integrity information attached, ready for remote review or a targeted retake request. Details on the Venta Capture field service page.