FDA's list of Paragraph IV patent certifications, updated Oct. 27, 2026, has 1,650 entries, according to the spreadsheet8 the agency posts on its patent certifications page5. Each entry is a drug product, down to dosage form and strength, for which at least one generic applicant has challenged a patent the brand listed with FDA. For 54 of them the first such application arrived in 2026, and for another 54 in 2025, by GxRadar's count of the list's submission dates.
The standard way such a fight starts is a single sentence in the generic company's application, asserting that the brand's patent is invalid or will not be infringed.
That sentence is a Paragraph IV certification. It is named after the paragraph of the 1984 Hatch-Waxman Act that describes it, now codified in section 505(j) of the Federal Food, Drug, and Cosmetic Act1, and it is the main legal route by which a generic reaches pharmacy shelves before the brand's last patent expires.
Filing one starts three fixed clocks. The generic has 20 days to notify the brand, the brand has 45 days to sue, and a timely suit triggers an automatic 30-month pause on FDA approval. How those clocks run, and how the resulting lawsuits tend to end, goes a long way toward explaining when a generic launches and how many versions are on the market in its first months.
Four certifications and a statement
Brand companies list certain patents for each approved product in FDA's Orange Book, described in GxRadar's Orange Book explainer. FDA's regulation on ANDA content, 21 CFR 314.942, requires a generic applicant to answer each listed patent with one of four certifications, each of which must carry its formal title, such as "Paragraph IV Certification."
| Certification | What the generic applicant states | Effect on approval timing |
|---|---|---|
| Paragraph I | No patent information has been filed for the brand drug | No patent barrier |
| Paragraph II | The listed patent has expired | No patent barrier |
| Paragraph III | The date on which the patent will expire, and the generic will wait | Approval takes effect when the patent expires; FDA can grant tentative approval before then |
| Paragraph IV | The patent is invalid, unenforceable, or will not be infringed by the generic | Approval can take effect before the patent expires, subject to notice, any lawsuit and any 30-month stay |
| Section viii statement | For a method-of-use patent, the generic is not seeking approval for the patented use and will leave it off its label | Lets the applicant avoid litigating that use patent (see our explainer on skinny labels and carve-outs) |
An applicant files one certification or statement per listed patent, so a single ANDA can contain several types. A generic might certify Paragraph III to a patent on the active ingredient that expires soon, and Paragraph IV to a later formulation patent it believes is invalid. FDA's page on patent certifications5 describes how the agency handles each.
Notice to the brand, on a 20-day clock
A Paragraph IV certification has to be delivered to the other side. Under the statute as amended by the Medicare Prescription Drug, Improvement, and Modernization Act of 20036, the generic applicant must notify the patent owner and the holder of the brand's application, explaining the factual and legal basis for its view that the patent is invalid or not infringed.
Timing is tightly controlled. FDA's rule at 21 CFR 314.953 says the notice must go out on or after the date the applicant receives FDA's paragraph IV acknowledgment letter, and no later than 20 days after that letter's postmark. A notice sent early does not count. The regulation states that it "is invalid if it is sent before the applicant's receipt of a paragraph IV acknowledgment letter."
How the 30-month stay works
Patent law treats the act of filing a Paragraph IV ANDA as a technical act of patent infringement, which lets the brand sue before the generic has sold anything.
If the patent owner sues within 45 days of receiving the notice, FDA's regulation at 21 CFR 314.1074 says the ANDA may be approved 30 months after the notice was received, unless a court shortens or extends that period. FDA can keep reviewing the application and grant tentative approval in the meantime. Since 2003, the automatic stay applies6 only to patents whose information was submitted to FDA before the ANDA was filed, so patents listed later cannot be used to stack new stays.
| Step | Timing |
|---|---|
| FDA sends the paragraph IV acknowledgment letter | Starts the notice clock |
| Generic sends Paragraph IV notice to brand and patent owner | Within 20 days of the letter's postmark |
| Patent owner decides whether to sue | 45 days from receipt of the notice |
| Automatic stay of approval, if suit is filed in time | 30 months from receipt of the notice |
| Stay when the brand holds new chemical entity exclusivity and the ANDA was filed in year four | Until 7.5 years after the brand's approval |
A stay can end early. Under the same regulation4, approval can take effect sooner if a district court rules the patent invalid, unenforceable or not infringed, if the court orders the stay shortened, or if the suit is dismissed without a finding of infringement. A settlement order or consent decree entered by the court stating that the patent is invalid, unenforceable or not infringed also clears the way. If the court instead finds infringement, approval waits until the date the court sets, usually the patent's expiration.
If the brand does not sue within 45 days, there is no stay. FDA can approve the generic once the application is otherwise ready and no exclusivity blocks it. GxRadar's guide to how a generic drug gets approved covers the rest of that review.
Inside the litigation
These cases are heard in federal district court. Because the generic has not launched, there are normally no sales on which to claim damages, and the cases are usually tried before a judge. The core questions are whether the generic product falls within the patent's claims and whether the patent is valid at all, for example because the invention was obvious when the patent was filed.
Appeals go to the US Court of Appeals for the Federal Circuit. Generic makers may also ask the Patent Trial and Appeal Board at the US Patent and Trademark Office to review a patent's validity in a separate proceeding. Under the Orange Book Transparency Act of 20207, a final decision there that cancels patent claims can lead to the patent's removal from the Orange Book.
How these cases end
Many Paragraph IV cases settle. A common settlement gives the generic a license to launch on a set date before the patent expires, which ends the uncertainty for both sides.
Settlements draw antitrust scrutiny when the brand pays the generic, in cash or other value, and the generic agrees to delay entry. These are known as pay-for-delay or reverse-payment settlements, the subject of GxRadar's piece on pay-for-delay settlements. Since the 2003 law6, a generic applicant with a Paragraph IV certification and the brand company must file such agreements with the Federal Trade Commission and the Justice Department within 10 business days of signing them.
Where the effect shows up
When a generic launches before the brand's last patent expires, the date usually traces back to a Paragraph IV case, either a court ruling or a settled entry date. The first company to file an ANDA with a Paragraph IV challenge may also earn 180 days of exclusivity, during which later Paragraph IV filers cannot be approved. The rule is in section 505(j)(5)(B)(iv)1 of the act, subject to forfeiture provisions added in 2003.
That exclusivity shapes how many versions reach pharmacies in the first months after launch, and the number of competitors in turn drives price, as GxRadar's piece on why generic prices fall as competitors enter shows. Year-by-year counts of first-time generic approvals are on the GxRadar approvals page.
Sources and notes
- Legal Information Institute (2026). 21 U.S.C. 355, New drugs (section 505 of the FD&C Act)
www.law.cornell.edu/uscode/text/21/355 - Legal Information Institute (2026). 21 CFR 314.94, Content and format of an ANDA
www.law.cornell.edu/cfr/text/21/314.94 - Legal Information Institute (2026). 21 CFR 314.95, Notice of certification of invalidity, unenforceability, or noninfringement of a patent
www.law.cornell.edu/cfr/text/21/314.95 - Legal Information Institute (2026). 21 CFR 314.107, Approval of a 505(b)(2) application or ANDA
www.law.cornell.edu/cfr/text/21/314.107 - FDA (2026). Patent Certifications and Suitability Petitions
www.fda.gov/drugs/abbreviated-new-drug-application-anda/patent-certifications-and-suitabil - Congress (2003). Public Law 108-173, Medicare Prescription Drug, Improvement, and Modernization Act of 2003
www.govinfo.gov/content/pkg/PLAW-108publ173/html/PLAW-108publ173.htm - Congress (2021). Public Law 116-290, Orange Book Transparency Act of 2020
www.govinfo.gov/content/pkg/PLAW-116publ290/html/PLAW-116publ290.htm - FDA (2026). Paragraph IV Patent Certifications list, as of October 27, 2026 (spreadsheet)
www.fda.gov/media/194880/download
Superscript numbers in the text link to these sources. GxRadar data (NADAC histories, recall and shortage counts) come from CMS and FDA files described on the sources page. Researched and drafted with AI assistance and checked against the sources above. Information current as of Nov 3, 2026 and may change. Spot an error? It will be corrected once confirmed.
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