Learning how to purchase a patent starts with the checks that eliminate most candidates, because they are free and they take minutes.
A substantial share of patents offered for sale are expired, encumbered, or held by someone whose chain of title has a gap in it.
Finding that out costs nothing. Finding it out after negotiating for six weeks costs the six weeks.
Five stages, and the second one does most of the work.
The five stages
| # | Stage | Time |
|---|---|---|
| 1 | Identify candidates | Variable |
| 2 | Verify status and ownership | Minutes, free |
| 3 | Diligence — claims, encumbrances, family | Days to weeks |
| 4 | Price and terms | Negotiation |
| 5 | Execute and record | Days |
Stage 1: finding candidates
| Source | Detail |
|---|---|
| Listing platforms | Widest reach, mixed quality |
| Brokers | Curated, buyer-side access |
| Auctions | Concentrated, time-boxed |
| Direct approach to owners | Frequently the best value |
| Bankruptcy and insolvency estates | Distressed pricing |
| Owners facing a maintenance fee | Motivated, often undecided |
Direct approach is undervalued. Many owners approaching a fee window have not decided what to do and have never considered selling, so an approach arrives as an option they did not have.
Identify them from fee due dates and non-practising status. Both are public.
Stage 2: verification
| Check | Source | Time |
|---|---|---|
| In force, fees paid | USPTO Patent Center | 3 min |
| Recorded owner | USPTO Assignment Search | 5 min |
| Remaining term | Front page + PTA | 5 min |
| Continuation chain | Related U.S. Application Data | 3 min |
| Terminal disclaimer | Front page | 2 min |
| PTAB history | PTAB records | 10 min |
Under half an hour, entirely free.
| Ipiry Patent Survival Curve v1.0 | Rate |
|---|---|
| Survive the 3.5-year fee (2022 cohort) | 85.8% |
| Survive the 7.5-year fee (2018 cohort) | 64.6% |
| Reach full term (2014 cohort) | 41.4% |
| Abandoned before full term | 58.6% |
Computed from 27,273,654 USPTO maintenance fee records covering 8,262,336 US utility patents — see the patent survival curve.
The continuation trap catches buyers. A patent filed in 2022 as a continuation of a 2014 application expires in 2034, not 2042 — eight fewer years than the filing date suggests. See patent status.
Stage 3: diligence
| Area | What to establish |
|---|---|
| Chain of title | Inventors → each transfer → current owner, no gaps |
| Security interests | Recorded, and released |
| Existing licences | Including exclusive ones, which may not be recorded |
| Employment and contractor assignments | Executed, present-tense language |
| Claims | What they actually cover |
| Evidence of use | Do they read on real products? |
| Prosecution history | Estoppel, surrendered scope |
| Family | Continuations, foreign counterparts |
| Litigation and PTAB | Past and pending |
Exclusive licences are the invisible encumbrance. They restrict what an owner can transfer and frequently appear nowhere in the record, so they have to be warranted rather than verified.
Read the prosecution history. Scope surrendered during examination is permanently gone, and it is free to check. See prosecution history estoppel.
Reading the chain
| Step | Check |
|---|---|
| 1 | Do the inventors assign to the first entity? |
| 2 | Does each assignor match the previous assignee? |
| 3 | Any gap between them? |
| 4 | Any entity in the chain now dissolved? |
| 5 | Security interests released? |
| 6 | Foreign jurisdictions recorded separately? |
Gaps have three causes — an unrecorded transfer, an unrecorded name change, or a transfer by a party that did not own it. The first two are fixable; the third may not be.
A dissolved entity in the chain is the hard case, because the party needed to execute a corrective assignment no longer exists. See assignment search.
Stage 4: pricing
| Approach | Use |
|---|---|
| Income | What the claims let you do or stop |
| Market | Comparables, where they exist |
| Cost | Weak — prosecution spend says little |
| Adjustment | Direction |
|---|---|
| Remaining maintenance fees | Subtract |
| Foreign annuities | Subtract |
| Documented evidence of use | Add substantially |
| Short remaining term | Discount heavily |
| Family depth | Add |
| Validity risk | Discount |
| Chain defects | Blocking, not discounting |
Subtract the fees you will inherit. They are a real cost of ownership, up to $14,470 for a large entity in the US alone plus annuities abroad.
| Fee | Due after grant | Large | Small | Micro |
|---|---|---|---|---|
| First | 3.5 years | $2,150 | $860 | $430 |
| Second | 7.5 years | $4,040 | $1,616 | $808 |
| Third | 11.5 years | $8,280 | $3,312 | $1,656 |
Note your own entity status. A micro entity buying from a large entity pays 20% of the remaining fees, which is a real part of the value. See small entity status.
Terms to negotiate
| Term | Position |
|---|---|
| Patents listed by number | Including continuations and foreign counterparts |
| Pending applications | Include or exclude explicitly |
| Warranty of ownership and authority | Ask for it |
| No undisclosed encumbrances or licences | Ask for it |
| Fees current at closing | Ask for it |
| Warranty of validity | Do not expect it |
| Seller licence back | Their request; assess it |
| Cooperation on recordation | Include |
| Files and prosecution records | Include |
Nobody warrants validity, and a seller who offers to is either inexperienced or pricing something you should look at more closely.
Get cooperation on recordation in writing. Foreign recordation frequently needs seller signatures after closing.
Stage 5: execute and record
| Step | Detail |
|---|---|
| Written assignment | Signed by the recorded owner |
| Record at the USPTO | Promptly |
| Record in each foreign jurisdiction | Separately |
| Verify recordation | Check the record afterwards |
| Update fee docketing | The fees are yours now |
| Update entity status | Yours, not the seller's |
Unrecorded foreign transfers block renewal payments. Several jurisdictions require the recorded owner to match, so an omission becomes a missed annuity and a lost patent. See patent annuity fees by country.
Worked example: two candidates
Both offered at similar prices.
| Candidate A | Candidate B | |
|---|---|---|
| Stated term remaining | "12 years" | 9 years |
| Actual term | 5 years — continuation of a 2013 parent | 9 years, verified |
| In force | Yes | Yes |
| Chain | Gap — an IP LLC appears from nowhere | Clean |
| Security interest | Recorded 2019, never released | None |
| Evidence claims read on products | None offered | Chart on 2 products |
| Foreign family | US only | US, EP, CN |
| Outcome | Declined | Purchased |
Candidate A failed on three counts, all found free in under an hour.
The term overstatement was not necessarily dishonest. Sellers miscalculate continuation chains routinely, which is why the buyer checks rather than accepts.
The unreleased security interest alone would have stopped it. A lender still appears on the record with an interest in the asset.
What you are actually buying
| You get | You take on |
|---|---|
| The right to exclude | Maintenance fees |
| Standing to enforce | Enforcement cost |
| The ability to license | Validity defence |
| The asset to resell | Administration |
A patent is an asset with a running cost. That is the whole reason 58.6% of them are abandoned by their owners.
Buy it because you will do something with it — practise, license, enforce, or block. Buying to hold is buying a liability.
How to purchase a patent: the checklist
- Verify in-force status first. Three minutes, free, eliminates many candidates.
- Check the recorded chain from the inventors forward.
- Treat any gap as blocking until documented.
- Look for unreleased security interests.
- Calculate term from the earliest parent, never the filing date shown.
- Ask for warranties on encumbrances and licences, which records cannot show.
- Do not expect a validity warranty. Nobody can give one.
- Subtract the maintenance fees you will inherit from the price.
- Record the assignment promptly, in every jurisdiction where rights exist.
- Buy only what you will use. Holding costs money every year.