Job costing and finance

Overbilling and underbilling explained with examples

Overbilling means you have invoiced more than the revenue you have earned on a job; underbilling means you have earned more than you have invoiced. Both come from comparing billed to date with earned revenue on the WIP report.

An office manager and contractor review invoices with a calculator and laptop in a construction office.
Review invoices, committed costs, and cash timing together before making project decisions. AI-generated illustration.

Overbilling happens when a contractor has billed a customer more than the revenue earned on a job so far. Underbilling is the opposite: more revenue earned than billed. You find both by taking billed to date and subtracting earned revenue, where earned revenue is the contract value times percent complete. A positive result is overbilling, which sits on the balance sheet as a liability (you owe the customer work). A negative result is underbilling, which sits as an asset (the customer owes you an invoice). Neither is automatically good or bad. What matters is the size, the trend, and the reason.

Accountants often call overbilling "billings in excess of costs and estimated earnings" and underbilling "costs and estimated earnings in excess of billings." Same idea, longer names.

How to calculate overbilling and underbilling

  1. Find percent complete. Cost to date divided by estimated total cost (the cost-to-cost method most contractors use).
  2. Find earned revenue. Contract value, including approved change orders, times percent complete.
  3. Find billed to date. Every invoice on the job through the same date, including retainage billed but held by the customer.
  4. Subtract. Billed to date minus earned revenue. Positive is overbilled; negative is underbilled.
  5. Book the adjustment. Your accountant records the result so revenue on the income statement matches earned revenue, not billings.

Overbilling example

Say a mechanical sub has an $800,000 contract with an estimated total cost of $680,000. By month end, it has spent $272,000 and billed $400,000 using a schedule of values that put heavy value on equipment and early rough-in.

Example: overbilled job
LineAmount
Contract value$800,000
Estimated total cost$680,000
Cost to date$272,000
Percent complete (272,000 / 680,000)40%
Earned revenue (800,000 x 40%)$320,000
Billed to date$400,000
Overbilling$80,000

The sub has $80,000 of the customer's money for work it has not done. If that cash is in the bank, fine. It will be needed, because the remaining 60 percent of the job carries $408,000 of cost but only $400,000 of billing left. If the $80,000 already paid for a truck or covered losses on another job, the company will be short at the back end of this one.

Underbilling example

Now a general contractor with a $1,200,000 contract and a $1,050,000 cost estimate. Cost to date is $525,000, and billing is $510,000.

Example: underbilled job
LineAmount
Contract value$1,200,000
Estimated total cost$1,050,000
Cost to date$525,000
Percent complete (525,000 / 1,050,000)50%
Earned revenue (1,200,000 x 50%)$600,000
Billed to date$510,000
Underbilling($90,000)

The GC has done $90,000 of work it has not invoiced. That may be harmless timing: a pay app cutoff on the 25th with costs through the 31st. It could be stored materials not yet billed, or signed change work not yet added to the pay app. Or it could be a warning. If the true estimated total cost is $1,120,000 and nobody updated the forecast, percent complete is overstated, earned revenue is overstated, and the "underbilling" is really a cost overrun wearing a disguise.

What overbilling and underbilling tell you

Common causes and what to check
PositionCommon causesWhat to check
OverbilledFront-loaded schedule of values, early deposits, billing for materials before cost postsIs the cash still in the bank? Is the cost to complete realistic?
UnderbilledBilling cutoff timing, unbilled change orders, stored materials, cost overrunsIs there billable work sitting unbilled? Did the estimated total cost move?
Swing month to monthLate cost posting, irregular billing, forecast not updatedAre costs and billings cut off on the same date?

Sureties and lenders tend to be comfortable with modest overbilling on well-run jobs, since it means the customer is funding the work. They get nervous about large or growing underbillings, because they are assets that may never turn into cash. A pattern of underbilled jobs that later fade in margin is one of the clearest risk signals on a WIP report.

How the accounting entries work

Most contractors bill through accounts receivable and record the invoice as revenue during the month. At month end, the accountant adjusts revenue to match earned revenue. For the overbilled job, revenue is reduced by $80,000 and a liability (often labeled billings in excess, or a contract liability) is recorded. For the underbilled job, revenue is increased by $90,000 and an asset (costs in excess, or a contract asset) is recorded. Next month the entry is reversed and recalculated. Your CPA will set the exact accounts; the point for operators is that the adjustment comes straight from the WIP numbers, so bad forecasts mean bad financial statements.

How to manage over and under billing month to month

The goal is not zero on every job. The goal is billing that tracks the work closely enough that cash and profit are both honest. A few habits get most contractors there.

  • Review underbilled jobs first. For each one, find the reason: timing, unbilled change orders, stored materials, or a forecast that has not caught up with cost. Bill what is billable this cycle.
  • Get change orders into the pay app fast. Signed change work left off the billing is the most common cause of avoidable underbilling.
  • Ring-fence overbilling cash. Some owners track it as a separate line in the cash forecast so it is not treated as free money.
  • Align cutoffs. Bill and post costs through the same date, or the numbers swing for no real reason.
  • Watch the trend, not the snapshot. One month of underbilling can be timing. Three months on the same job is a conversation with the PM.

Lenders and sureties notice the companies that do this. Steady, explainable positions on every job make the whole financial statement more believable.

Mistakes to avoid

  1. Spending overbilling cash as if it were profit.
  2. Assuming underbilling is conservative accounting rather than checking for overruns.
  3. Leaving retainage out of billed to date, which makes every job look underbilled.
  4. Cutting off billings and costs on different dates.
  5. Netting over and under billings across jobs and calling the company balanced.
  6. Front-loading the schedule of values so hard that the last third of the job runs on empty.

Templates and related reading

The WIP report template calculates both positions for every open job. For the full report, see how to read a construction WIP report. To keep billing aligned with work, read how to build a schedule of values, and for the forecast that drives percent complete, how to calculate cost to complete. Related terms: percentage of completion method and front-loading.

Smart Business Automator calculates over and under billing per job from live costs and billings, so the month-end adjustment is ready when the books close. See job costing and WIP automation.

Frequently asked questions

Is overbilling illegal?

No. In this accounting sense, overbilling just means billing has run ahead of earned revenue, often because of the schedule of values or deposits. It is different from billing for work you did not do, which is a contract and possibly a fraud problem.

Is overbilling an asset or a liability?

A liability. The company has received or billed money for work it still owes the customer. Underbilling is an asset.

Why is underbilling a red flag for sureties?

Because it is revenue recorded but not invoiced. If it comes from an outdated cost forecast, it may never be billed, and the profit behind it will reverse.

Do small contractors need to track over and under billing?

If you use percentage of completion accounting, prepare financial statements for a bank or surety, or run jobs longer than a month or two, yes. It is also the simplest way to spot jobs where billing and work have drifted apart.

Written and edited by

Maurice Francois writes and edits construction operations guides for Smart Business Automator. More from Maurice on the Scaling Legends podcast.

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