Sooner or later a customer, a distributor, or a general contractor hands a machine shop or manufacturer a contract with a line in it that says they must be named as an additional insured on your policy. It is one of the most common insurance requirements in manufacturing, and one of the least understood. An additional-insured endorsement adds another party as an insured under your liability coverage — so that, for the work or the products the contract covers, your policy can respond on their behalf too. This post explains what that means, which real endorsements do the work, and why one of them matters far more to a manufacturer than the other.
The short version: additional-insured status is added by a real endorsement to your general liability, not by the certificate of insurance that proves it exists. The two endorsements that matter for a manufacturer are, in ISO’s system, along the lines of CG 20 10 for ongoing operations and CG 20 37 for completed operations — and for someone who ships a product, the completed-operations one is the piece that counts. The coverage these endorsements extend is the products-liability side of general liability; this post explains which endorsement does what and why the distinction decides whether your customer is actually covered for your product after it ships.
What an additional insured is
An additional insured is a party added as an insured under your liability policy, so that your coverage can respond on their behalf for claims connected to your work or your products. The reason the request shows up so often in manufacturing is structural: your product moves up a chain. A part you machine goes into a customer’s assembly; a finished good you make is resold by a distributor; a component you supply ends up in a general contractor’s project. Each of those parties carries some risk that your product or work causes a third-party claim, and each of them, reasonably, wants your policy to stand in front of theirs when it does.
So they require it by contract. The requirement is almost never a handshake — it is a clause in a supply agreement, a purchase order, or a master services contract, and it usually comes paired with a demand for a certificate of insurance evidencing it. What a manufacturer has to understand is that the clause is asking for two related but different things: a real endorsement on the policy that grants the status, and a certificate that proves the endorsement exists. The endorsement is the coverage. The certificate is only the evidence.
The real endorsements: CG 20 10 versus CG 20 37
When a contract asks you to add an additional insured to your general liability, the coverage is granted by a specific endorsement attached to the policy. In ISO’s system, the two that matter for a manufacturer are, along the lines of, CG 20 10 and CG 20 37 — and the difference between them is the whole point.
CG 20 10 adds an additional insured for ongoing operations — it extends coverage to the named party for claims arising while the work is still in progress. CG 20 37 adds an additional insured for completed operations — the products-completed operations tail, the period after the product has shipped or the work is done. They are not interchangeable, and they are not a matched set you automatically get together. A policy can carry one without the other, which means a customer can hold an endorsement that covers them for the wrong window entirely. Editions and exact forms vary by carrier, so the form number written into a contract is a starting point to confirm against the policy, not proof of what is actually on it.
Why completed-operations status is the one that matters
For a manufacturer, the completed-operations endorsement is almost always the one that matters, and the reason is the nature of what you ship. Your product keeps existing after it leaves your control — installed, used, resold, and relied on — and a defect in it can surface as a third-party claim a long time later. A customer who buys from you wants their additional-insured status to reach that period: after delivery, after the work is done, when the product is out in the field. That is exactly the window an ongoing-operations endorsement does not reach, and exactly the window completed-operations status — the CG 20 37 endorsement — is built around.
This is the same products-completed operations exposure that general liability is built around, and the same one an umbrella adds limit over: the harm a defective product causes once it is out in the world. We keep that harm carefully distinct from recall expense and pure financial loss in the three products coverages, distinguished — and the additional-insured endorsement extends only that harm side, the third-party bodily injury and property damage, to the customer. It does not hand them your recall coverage or your errors-and-omissions line. So when a contract asks for additional-insured status “for completed operations,” it is asking to be brought onto the one part of your program that answers for the product after it ships.
Additional insured is not a certificate of insurance
The most common and costly mistake here is treating the certificate of insurance as the coverage. It is not. A certificate is a snapshot that evidences coverage exists; the additional-insured status is granted by the endorsement attached to the policy — along the lines of CG 20 10 or CG 20 37 — not by the certificate that references it. A customer who holds only a certificate, with no endorsement actually on the policy, may not have the coverage they believe they do, and a manufacturer who hands one over without confirming the endorsement is on the policy can be promising something the policy does not deliver.
The order that protects everyone is the same every time: confirm the endorsement is on the policy, confirm it reaches the operations the contract requires — ongoing, completed, or both — and then let the certificate evidence it. If you want the broader line between the products-liability harm an additional insured is brought onto and the rest of what general liability does, products liability vs general liability draws that distinction in full.
Why it matters for your operation
If you ship a product, additional-insured requirements are not paperwork to wave through — they are a description of where your customer expects your policy to stand in front of theirs, and getting the endorsement wrong leaves a gap that surfaces during a claim, not before. The completed-operations piece is usually the one that counts, because the exposure a customer is worried about begins the moment your product is in their hands and the work is done. We read what the contract actually requires, set the endorsement and certificate language to match, and confirm the status reaches the products tail rather than just the time you were on the job. When a customer or distributor lands a certificate request with additional-insured language you do not recognize, that is a call we take. Start with a quote and tell us what you ship, or read the full general liability page to see how the products-completed operations side the endorsement extends actually works. Editions and exact forms vary by carrier, so the right move is always to confirm what your policy actually carries rather than assume.