Guides / Process
What an Inspection and Test Plan Actually Covers
September 30, 2026
A quote for a large machined part usually comes with a drawing and a set of tolerances. For work going into regulated or safety related equipment, buyers often ask for something more: a document that says exactly what gets checked, at what point in the build, and who has to sign off before the next step happens. That document is the inspection and test plan, usually shortened to ITP.
What an ITP is
An ITP is a table, built before machining starts, that lists every inspection or test point in the sequence of making a part: material certification, dimensional checks at rough machining, non-destructive testing after heat treatment, final dimensional inspection, coating checks, and so on. Against each point it records the method, the acceptance criteria, and who is responsible for it.
The part that makes an ITP different from a normal quality process is the categorisation of each point into one of three types.
- Witness point. The buyer or their representative has the right to be present, but work can continue if they choose not to attend.
- Hold point. Work cannot continue past this point until the buyer has reviewed and approved the result, whether or not they attended in person.
- Review point. Documented after the fact, with no requirement to attend or approve in real time, usually for lower risk checks.
Why regulated buyers ask for one
On a bracket or a fixture, a final inspection report is normally enough: it proves the finished part is correct. On a large fabricated frame going into a power generation project, or a pressure retaining component in oil and gas type work, the concern is not only whether the final part is correct. It is whether every step that could have introduced a hidden problem, a missed heat treatment cycle, a weld that was never tested, a material substitution, was actually checked at the time it happened rather than assumed afterward.
An ITP creates that record as the part is built rather than reconstructing it later from memory. For a buyer answering to their own customer or to a certifying body, that traceability is often the actual deliverable, as important as the part itself.
What a typical ITP covers on a large machined part
The specific stages vary by part, but a plan for a large fabricated and machined component commonly includes:
| Stage | Typical check | Common point type |
|---|---|---|
| Incoming material | Certification review against EN 10204 or equivalent | Review |
| Welding, if fabricated | Visual and NDT per the applicable procedure | Hold or witness |
| Post weld heat treatment | Time and temperature record | Review |
| Rough machining | Dimensional check for stock allowance | Review |
| Semi-finish stage | Critical dimension and datum check | Witness |
| NDT after finish machining | Surface or volumetric testing as specified | Hold |
| Final dimensional inspection | Full report against drawing | Hold |
| Coating or preservation | Thickness or coverage check | Review |
These are typical stages, not a fixed template. A part with no welding drops the weld related rows, a part with no NDT requirement drops those, and a buyer with less at stake may agree to fewer hold points to keep the schedule moving.
Building one without slowing the quote down
An ITP is easiest to price correctly when it is drafted before the RFQ goes out rather than negotiated after a shop has already quoted. A shop pricing hold points it did not know about is either guessing at the cost or, worse, absorbing it and then asking for more once the job is underway.
A workable approach: state in the RFQ that an ITP is required, list any hold points you already know you need (typically final dimensional and any NDT stage), and let the shop propose the rest based on their own process. Agree the final plan before work starts, not after the first hold point comes due.
What to do next
If you are not sure whether the part actually needs a full ITP or just a solid final inspection report, that is worth deciding before the RFQ goes out rather than mid-quote, since it changes both the price and the schedule.
Related reading: how large machined parts are inspected, what to put in a large part RFQ, and the power generation industry page for the kind of work that most often carries a formal ITP requirement.
Frequently asked questions
Is an ITP the same thing as a first article inspection?
No. A first article inspection is a single report proving one finished part meets the drawing. An ITP is the plan that says what gets checked at each stage of making the part, who checks it, and which of those checks the buyer wants to witness or approve before work continues. The FAI report is usually one of the records an ITP calls for.
Who normally asks for an ITP: is it needed for every large part order?
There is no fixed rule, but it shows up most often on parts going into regulated or safety related equipment, such as power generation, pressure equipment or classed marine work, where a customer or a certifying body needs a documented chain of checks rather than just a final report. A one-off bracket rarely needs one.
What happens if a shop misses a hold point?
That depends on the plan and the contract behind it, so it should be spelled out before work starts rather than assumed. Some plans require the work to stop and the missed point to be reviewed before continuing, which can mean cutting into or re-verifying material already machined. Agree the consequence in writing, not after the fact.
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