Glossary
Not-to-exceed overrun
A not-to-exceed overrun is an invoice or billing total that exceeds a contract's NTE cap and gets paid without the cap being enforced. Read the full guide.
Margin drift is the gap between what a vendor contract says and what the invoice actually charges. A not-to-exceed overrun is one specific shape that drift takes: a contract states a ceiling on billing, usually as a total dollar cap on a phase, project, or statement of work, and the vendor bills past it anyway.
The term shows up most in professional services, IT projects, and contract labor, where hours are estimated up front and a cap is written in to protect the buyer from open-ended billing. When the cap is not actively checked against cumulative invoices, it stops functioning as a ceiling and becomes a number on a page.
1. What is a not-to-exceed overrun?
A not-to-exceed overrun is invoiced billing that exceeds the NTE cap stated in a contract, purchase order, or statement of work. The cap is written as a hard ceiling, not an estimate. An overrun means cumulative invoices crossed that ceiling and were paid without a change order or written approval documenting why the cap no longer applied.
The overrun is a payment event, not just a contract violation on paper. It happens the moment AP releases payment on an invoice, or a series of invoices, that push the running total past the stated cap.
The gap can be small and incremental, a few percent over on each of several invoices, or a single large invoice that jumps past the cap outright. Either pattern has the same effect: money left the business that the contract said should not.
2. Why does an NTE overrun happen if the cap is in the contract?
An NTE overrun happens because the cap lives in the contract or statement of work, not in the purchase order or the AP system that actually processes payment. Invoice review checks price and quantity against the PO. It does not sum invoices against a dollar ceiling written in a separate document, so the cap can be crossed while every individual invoice still looks correctly priced.
A purchase order is often issued at the estimated project value, and that PO amount gets revised as work continues. The NTE clause is a separate, fixed number that is not supposed to move with the estimate.
When cumulative billing is not tracked against that fixed number, each invoice can pass review on its own terms: correct hourly rate, correct quantity, matching PO. None of that catches a total that has quietly walked past the contractual ceiling.
- Cumulative tracking gap: Invoice review is typically done invoice by invoice, not as a running total against the contract's lifetime cap.
- PO drift from the NTE: A purchase order gets revised upward to match spend, while the underlying NTE clause stays fixed and unreferenced.
- Separate document, separate owner: The cap sits in a contract the contract owner holds. AP holds the invoice. Neither view contains both pieces at once.
3. How does three-way matching handle NTE overruns?
Three-way matching checks that the invoice, purchase order, and receipt of goods or services agree with each other. It confirms quantity and unit price line up across those three documents. It does not read the NTE clause in the master service agreement or statement of work, so a cumulative total above the cap can match cleanly on all three points and still be paid.
This is a structural gap, not a failure of the control. Three-way matching was built to confirm that what was ordered, delivered, and billed are the same thing. A contractual ceiling on total spend across a project is a different kind of check, one that requires summing invoices over time against a document the matching process never opens.
Closing that gap means someone, or some system, tracks cumulative billing against the NTE cap separately from the line-item match. That is a contract compliance function, not an AP function.
4. How is an NTE overrun different from scope creep?
Scope creep is work expanding beyond what the statement of work originally defined, and it may or may not cross a dollar cap. A not-to-exceed overrun is specifically about the cumulative invoice total exceeding the stated ceiling, whether or not the underlying scope changed at all. A project can overrun its cap on unchanged scope, just underestimated hours.
The two often travel together. Expanded scope is a common reason a project reaches its cap early, and a vendor delivering added scope without a change order is also usually the vendor billing past the cap without one.
They are worth separating in review because the fix differs. Scope creep is addressed by tightening the statement of work and change order discipline. An NTE overrun is addressed by tracking cumulative spend against the cap directly, independent of whether scope moved.
For the wider pattern this sits inside, start with the margin drift guide. See also off-contract resources: people billed outside the agreement and unapplied volume rebates in staffing agreements.
Common questions
What is a not-to-exceed overrun?
A not-to-exceed overrun is an invoice, or a run of invoices, that pushes total billing past the NTE cap stated in a contract or statement of work. The cap is meant to be a hard ceiling. An overrun means it was crossed and paid rather than stopped or escalated for approval.
Is an NTE cap the same as a purchase order amount?
No. A purchase order amount is often set from an estimate and gets revised as spend grows. An NTE cap is a contractual ceiling meant to hold regardless of the estimate. Confusing the two is one reason overruns get paid: the PO looks fine even after the NTE has been passed.
Why does three-way matching miss NTE overruns?
Three-way matching checks the invoice against the purchase order and the receipt of goods or services. It confirms quantity and unit price agree across those three documents. It does not read the NTE clause in the underlying contract, so a cumulative total above the cap can still match cleanly on all three points.
Where does an NTE cap usually appear?
It typically sits in the pricing or payment section of a master service agreement or a statement of work, sometimes as a single ceiling and sometimes broken out by phase or milestone. It can also appear as a standalone clause referenced by the purchase order.
Can an NTE cap be exceeded legitimately?
Yes, if the contract includes a change order process and that process was followed: written approval, a revised cap, and a documented reason. An overrun is the same dollar event without that paper trail. The difference is procedural, not the size of the amount.
Which vendor categories carry NTE clauses?
NTE clauses appear in professional services statements of work, IT project contracts, and some contract labor and staffing agreements, wherever hours or scope are estimated up front and the buyer wants a billing ceiling written in.
How is an NTE overrun different from scope creep?
Scope creep is work expanding beyond what was originally defined, which may or may not cross a dollar cap. An NTE overrun is specifically about the cumulative invoice total exceeding the stated ceiling, whether or not the underlying scope changed.
Who is responsible for catching an NTE overrun before it is paid?
Responsibility usually sits between the contract owner, who knows the cap, and AP, who processes the invoice. Neither party alone typically has both the contract detail and the payment visibility needed to catch the overrun before payment goes out.
ValueXPA runs a fixed-scope Margin Drift Diagnostic that validates every service vendor invoice against contract terms. Two to four weeks, and you keep 100% of what is recovered.
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