Spotting Subcontractor Overbilling: Padded Labor, Inflated Quantities, Phantom Work
Every general contractor has paid for work that was not done. Not because anyone signed off on a fraudulent invoice, but because a subcontractor billed 60% complete on a line that was closer to 45%, and nobody had the time or the jobsite knowledge to push back. By the time the discrepancy surfaced — if it ever does — the money is gone, the retainage has been released, and the sub has moved on to the next project.
Subcontractor overbilling sits in an uncomfortable gray zone. A small fraction of it is deliberate fraud. Most of it is what you might generously call optimistic billing: a sub who is short on cash bills ahead of progress to improve their own working capital, fully intending to catch up. The problem is that optimistic billing and fraudulent billing look identical on a pay application. The only thing that separates a contractor who catches it from one who does not is a disciplined review process that compares what is billed against what actually exists on the jobsite.
Roughly 0 in 5
Share of organizations' fraud losses attributed to billing schemes, the most common occupational fraud category (ACFE Report to the Nations)
Overbilling is not one behavior. It shows up in distinct patterns, and each one is caught by a different check. If your review process only looks for one form, you will miss the other three.
On time-and-materials work and on change orders billed by labor, the most direct form of overbilling is hours that were never worked. A crew of six is billed as a crew of eight. A foreman who spent half a day on another job is billed full-time. Overtime is claimed for hours worked at straight time. Padded labor is hardest to catch on cost-plus and T&M work precisely because there is no fixed scope to measure against — the bill is whatever the timesheets say, and the timesheets are produced by the party being paid.
Unit-price work invites quantity inflation. A sub installs 1,800 linear feet of conduit and bills 2,100. They pour 340 cubic yards and bill 380. Each individual overstatement is small enough to fall inside the noise of a busy project, but across a schedule of values with dozens of unit-price lines, the cumulative effect is significant. Quantity inflation also appears on excavation, fill, demolition, and anything else measured rather than counted — categories where the as-built quantity is genuinely hard to verify after the fact.
Stored-materials billing is a legitimate practice — a sub buys steel or switchgear in advance and bills for it before installation. It is also a common overbilling vector. The sub bills for materials that were never purchased, were purchased but delivered to a different job, or were delivered in a smaller quantity than billed. Stored-materials lines deserve scrutiny because, unlike installed work, you cannot confirm them by walking the building. You confirm them with delivery tickets, bills of sale, and proof that the material is insured and stored on or near the site.
The most structural form of overbilling happens before a single pay application is submitted — when the schedule of values is built. A sub loads disproportionate value into early activities (mobilization, submittals, demolition, rough-in) and underweights the finish work that comes at the end. Every dollar billed is technically for real work, so no single pay app looks wrong. But the sub is collecting cash faster than they are earning it, which means that if they walk off the job at 70% complete, they may have already been paid 85% of their contract. The contractor is left to finish the work with less money than the remaining scope costs.
Front-loading is the overbilling pattern that does the most damage in a default scenario. Review the schedule of values for reasonableness when it is first submitted — before it is approved — because once it is locked in, every pay application built on it will look perfectly legitimate.
If overbilling were obvious, it would not be a problem. Several structural features of construction billing make it genuinely difficult to detect with a normal AP review.
The conditions that let overbilling pass:
- Percent-complete billing is inherently a judgment call — a line that is 'about half done' can be billed at 50% or 60% and neither is provably wrong from a desk
- The person who can verify progress (the project manager or superintendent) is on the jobsite, not in the AP office, and is rarely looped into the pay-app review
- Pay applications arrive monthly under deadline pressure, and a 40-line G703 continuation sheet gets a cursory scan, not a line-by-line audit
- Retainage masks the problem — a 10% holdback feels like a safety margin, so a 5-10% overbill seems covered even when it is not
- Each month's overbill is small; the pattern only becomes visible when you look at the trend across several pay periods
- Subs who overbill are often the ones doing the most work, so there is reluctance to challenge a key trade partner over a few percentage points
Detection does not require forensic accounting. It requires a handful of specific comparisons, done consistently on every pay application, with the right person involved at the right step.
The single most important check is also the simplest: before a pay application is approved, the project manager or superintendent who walks that scope confirms the billed percentage against what they actually see in the field. This cannot be done from the AP office. It is a field judgment, and the pay-app workflow has to route the document to the field for that judgment rather than treating the PM's approval as a rubber stamp. A PM who is asked specifically — 'the drywall sub billed 65% on Building B, is that right?' — will catch an overbill that the same PM would have approved if handed the whole pay app with no prompt.
Get AP insights in your inbox
A short monthly roundup of construction AP + accounting posts. No spam, ever.
No spam. Unsubscribe anytime.
For unit-price work and stored materials, billed quantities should reconcile to an independent record: delivery tickets, weigh tickets, survey measurements, or installed counts from the field. A conduit line billed at 2,100 linear feet should be supported by material that was delivered and a field measurement that confirms it. If the only evidence for a quantity is the sub's own pay application, the quantity is unverified — and unverified quantities on measured work are exactly where inflation lives.
Every billed line should be priced at the contract unit rate. It sounds elementary, but rate drift is common: a change order gets billed at a higher rate than the base contract, or a unit price creeps up between pay periods. Compare the effective rate on each line — dollars billed divided by quantity billed — against the contracted rate. A line where the math does not tie is either a clerical error or a quiet rate increase, and both need an explanation before the line is paid.
Documentation is the difference between an opinion and a finding. Progress photos timestamped to the billing period, delivery tickets for stored materials, and signed daily reports turn 'I think the sub overbilled' into 'the pay app claims 70% but the photos from the cutoff date show framing only.' Require photo backup for any line where the billed percentage jumps significantly, and require delivery tickets and proof of payment for every stored-materials line. Subs who know that stored-materials billing triggers a document request bill those lines far more conservatively.
A single pay application cannot reveal front-loading or a slow-building overbill. The trend can. Track each sub's cumulative billed percentage against the project schedule's expected percentage over time. A sub who is consistently billing 10-15 points ahead of schedule progress is either front-loaded or overbilling, and the gap is your early warning. Watch especially for the sub whose billing races ahead in the first third of the job and then stalls — that is the classic signature of a front-loaded schedule of values catching up with reality.
This is where automation earns its keep. A platform like Covinly can hold every line of a G703 against the contract schedule of values, recompute unit rates, surface lines that jumped since the prior pay app, and chart cumulative billing against schedule progress — so the review starts from the three or four lines that actually need a human judgment, not from a blank 40-line spreadsheet.
Catching an overbill is only useful if you handle it well. The instinct to either ignore it (to keep the peace) or escalate it to an accusation (because it feels like fraud) are both wrong more often than they are right.
Start by treating it as a billing discrepancy, not a crime. Most overbilling is a cash-flow move, not a theft, and an opening posture of 'your pay app shows 65% on this line and our field walk shows about 50% — can you walk us through it?' gives a sub who simply billed optimistically a graceful way to correct it. Adjust the current pay application down to the verified percentage before it is paid. Do not pay the disputed amount and chase it later; recovering an overpayment from a sub is far harder than declining to make it.
Document the adjustment and the reason. A pattern matters: a sub who overbills once and corrects cleanly is different from a sub who overbills every month and argues every adjustment. The second pattern is where you tighten controls — more frequent field verification, mandatory photo backup, stored-materials documentation on every line — and where you involve your project executive and, if the numbers warrant it, your risk or legal function. Persistent, deliberate overbilling, especially combined with unsupported stored materials or phantom labor, can cross into fraud, and at that point it is no longer an AP conversation.
“We stopped treating the pay-app review as a paperwork step and started treating it as a field verification. The month we began routing every continuation sheet to the superintendent with the three highest-percentage lines flagged, our first-pass adjustments tripled — and within a quarter the subs were billing tighter because they knew we were actually looking.”
— Project executive, regional general contractor
Subcontractor overbilling is not exotic, and catching it does not require suspicion of your trade partners. It requires a review process that does three things every month: compares billed percentages to what a knowledgeable person sees on the jobsite, ties quantities and rates to independent records, and watches the billing trend across pay periods rather than judging each pay application in isolation. Do those three things consistently and the optimistic billing corrects itself — because subs bill conservatively when they know the contractor is checking, and they bill ahead when they know nobody is.
Written by
Marcus Reyes
Construction Industry Lead
Spent twelve years running AP at a $120M general contractor before joining Covinly. Lives in the world of AIA G702/G703, retainage schedules, and lien waiver deadlines. Writes about the construction-specific workflows that generic AP tools get wrong.
View all posts