What is Work in Progress in Services?

Between the hour that was worked and the invoice that was raised sits the most quietly dangerous number in a people business. It looks like an asset, it is booked as an asset, and it behaves like an asset right up until the moment someone has to defend it to a client, at which point a portion of it turns out to have been hope.

Delivered, but not yet billed

Work in progress in services is delivered effort that has not yet been invoiced: recorded time, usually carried at billing value, plus unbilled expenses. In manufacturing, WIP is physical, half-built goods you can walk past and count. In services it is a promise resting on two different certainties. The cost is fully real: the salaries funding those hours were paid in the month they were worked. The revenue is not yet real: it is an expectation that the client, when the bill finally arrives, will agree the work was asked for and worth it. The arithmetic is simple, and the numbers here are invented purely to illustrate it. A team records four hundred unbilled hours on an engagement at a billing value of one hundred and eighty per hour: seventy two thousand of WIP. The cost of those hours has already left the building. The seventy two thousand has not arrived, and until an invoice exists it is not even a claim, only an intention.

Ageing WIP is an early warning

Fresh WIP is normal; work is always slightly ahead of billing. The information is in the age. WIP that sits unbilled for months is telling you one of a few things: the billing process is slow, which is benign; the scope is disputed and nobody wants to force the question; the team itself doubts the work is chargeable, which is scope creep confessing on the balance sheet; or somebody is avoiding a conversation. Meanwhile the asset decays. The client’s memory of the value fades, the people who asked for the work move on, and an invoice that consolidates a quarter of accumulated effort reads as an ambush rather than a record. Ageing WIP is the balance sheet remembering a conversation the firm has been avoiding. That is what makes a WIP ageing report one of the best leading indicators in the business: it surfaces margin damage while it is still, technically, recoverable.

The write-off conversation arrives too late

Every firm that carries WIP eventually holds the meeting: quarter end, the ageing report, a partner deciding how much of the balance to release as invoices and how much to write off. The meeting is framed as billing hygiene. It is actually the formal recording of decisions that were made months earlier, informally, by whoever kept accepting work outside a clear agreement without choosing between invoicing it, papering it, or absorbing it. By the time the write-off review convenes, the options have expired: the moment to raise a change order was when the extra work was requested, and the moment to bill was when the value was fresh. The write-off simply crystallises revenue leakage that happened gradually and invisibly, then books it all on one honest, painful day.

One concrete example

Clearly illustrative, with invented round numbers and no customer implied. An engagement bills monthly against an agreed scope. From the second month, the client’s team starts asking for small extras: an additional report, an integration tweak, an extended workshop. Each is accepted verbally and recorded as time, none is billed, and the unbilled balance builds quietly for three months. At the quarterly WIP review, the accumulated extras are worth a figure large enough that invoicing it in full would shock the client. The partner splits the difference: a partial invoice, a substantial write-down, and a note to be firmer next quarter. Nobody can reconstruct which requests made up the balance, who accepted them, or what was said, because none of those acceptances was ever recorded as a decision. The engagement’s delivered margin absorbs the loss, and the pattern repeats.

The decision WIP should trigger

The durable fix is to move the decision to where the risk is created. Work performed outside a clear agreement is a choice with three options: invoice it, convert it into a papered change, or absorb it knowingly with the cost recorded and a reason attached. Taken at the moment the work is accepted, each option is cheap; deferred a quarter, only the worst one remains. A practical discipline follows: WIP crossing an age threshold triggers a named decision with a named owner, not a line on a review pack. That is the decision-intelligence reading of WIP: the balance is not a financing quirk but a queue of unmade decisions, each ageing toward its most expensive resolution. Recorded properly, with who chose and against what evidence, those decisions become a pattern the firm can learn from: which clients, which teams and which kinds of work generate WIP that decays, and where the engagement-grain numbers should be watched hardest. The write-off meeting still happens. It just stops containing surprises.