# patentreply.ai > Patent tools and reference content for patent attorneys, agents, and pro-se applicants. Free calculators for patent expiration, assignment lookups, and application monitoring, plus in-depth guides written against the U.S. patent statute (35 U.S.C.), the Code of Federal Regulations (37 CFR), the MPEP, and Federal Circuit case law. All content is written to be cited. Each guide links its primary statutory and case-law sources, includes worked examples with concrete numbers and dates, and carries a last-reviewed date. Informational only; not legal advice. ## Tools - [Patent Expiration Calculator](https://www.patentreply.ai/tools/patent-expiration): Calculate U.S. utility patent expiration dates with earliest effective filing date analysis, PTA, and terminal disclaimer caps. - [Patent Assignment & Ownership Lookup](https://www.patentreply.ai/tools/patent-assignment): Retrieve and summarize USPTO assignment records for a patent or application. - [Office Action Intelligence](https://www.patentreply.ai/tools/office-action): Paste a U.S. patent application number and get a structured, plain-English read of every Office Action on the case — rejection grounds (§101, §102, §103, §112), prior art consulted, claim status, prosecution timeline, and current USPTO application status. - [Application Monitor](https://www.patentreply.ai/tools/monitors): Track U.S. patent applications and receive email alerts for major USPTO status changes. ## Patent Expiration Guides to U.S. utility patent term: 20-year baseline, PTA, PTE, terminal disclaimers, continuations, and maintenance fees. - [Patent Expiration hub](https://www.patentreply.ai/tools/patent-expiration) - [When Does a Patent Expire? A Complete Guide to Patent Term](https://www.patentreply.ai/patent-expiration/when-does-a-patent-expire): Comprehensive overview of U.S. patent term rules, the 20-year baseline, and common adjustments. - [How to Calculate Patent Expiration for Continuations and Divisionals](https://www.patentreply.ai/patent-expiration/continuation-and-divisional): How the earliest effective filing date is determined across continuation and divisional patent families. - [How Terminal Disclaimers Affect Patent Expiration](https://www.patentreply.ai/patent-expiration/terminal-disclaimers): What terminal disclaimers are, when they apply, and how they can cap a patent's effective term. - [Patent Term Adjustment vs Patent Term Extension](https://www.patentreply.ai/patent-expiration/pta-vs-pte): The key differences between PTA (prosecution delays) and PTE (FDA regulatory delays). - [How to Find the Earliest Effective Filing Date](https://www.patentreply.ai/patent-expiration/earliest-effective-filing-date): Step-by-step guidance on tracing the priority chain to identify the controlling filing date. - [Applicant Delay and PTA Reductions](https://www.patentreply.ai/patent-expiration/applicant-delay-pta-reductions): How the 3-month reply rule, IDS timing, and post-allowance papers under 37 CFR 1.704 reduce PTA. - [How to Verify and Challenge USPTO PTA Calculations](https://www.patentreply.ai/patent-expiration/verify-pta-calculations): How to check the USPTO's PTA math and request reconsideration under 37 CFR 1.705(b) within the 2-month window. - [RCEs and Patent Term: The B-Delay Trade-Off](https://www.patentreply.ai/patent-expiration/rce-patent-term-impact): How filing an RCE excludes time from B-Delay under § 154(b)(1)(B), with trade-offs against appeal. - [Double Patenting, PTA, and Patent Families](https://www.patentreply.ai/patent-expiration/double-patenting-pta): How obviousness-type double patenting interacts with PTA after In re Cellect and the Allergan safe harbor. - [Maintenance Fees and Patent Expiration](https://www.patentreply.ai/patent-expiration/maintenance-fees): The 3.5/7.5/11.5-year deadlines, grace periods, revival, and intervening rights under 35 U.S.C. § 41(b). ## Patent Assignment Guides to USPTO patent assignment records: ownership, chain of title, security interests, and recording mechanics. - [Patent Assignment hub](https://www.patentreply.ai/tools/patent-assignment) - [How to Find the Owner of a Patent](https://www.patentreply.ai/patent-assignment/how-to-find-patent-owner): A guide to using USPTO assignment records to identify who appears to own a patent. - [What Is a Security Interest in a Patent?](https://www.patentreply.ai/patent-assignment/security-interests): How security interests work in patent records and why they differ from ownership transfers. - [How to Read USPTO Patent Assignment Records](https://www.patentreply.ai/patent-assignment/how-to-read-assignment-records): Step-by-step guidance on interpreting the sequence of recorded assignment events. - [Patent Assignment vs Patent License](https://www.patentreply.ai/patent-assignment/assignment-vs-license): The key differences between transferring patent ownership and licensing patent rights. - [Patent Chain of Title Explained](https://www.patentreply.ai/patent-assignment/chain-of-title): What chain of title means for patents and why it matters in diligence and transactions. - [What Does Reel and Frame Mean in Assignment Records?](https://www.patentreply.ai/patent-assignment/reel-and-frame): How the USPTO organizes recorded assignment documents using reel and frame numbers. - [Patent Ownership Due Diligence Checklist](https://www.patentreply.ai/patent-assignment/due-diligence-checklist): Key steps for reviewing patent ownership as part of an acquisition or investment. - [Can You Search Patent Assignments by Application Number?](https://www.patentreply.ai/patent-assignment/search-by-application-number): How to look up assignment records using an application number instead of a patent number. ## Reference - [Glossary](https://www.patentreply.ai/glossary): Plain-English definitions of patent-law terms used across the guides, each linked to the controlling statute, regulation, or precedent. Emitted as schema.org DefinedTerm entities. - [Documentation](https://www.patentreply.ai/documentation) - [FAQ](https://www.patentreply.ai/faq) - [Sitemap](https://www.patentreply.ai/sitemap.xml) ## About patentreply.ai is a patent tools platform. Guides are authored by the patentreply.ai editorial team and are reviewed on a rolling basis. For the primary legal sources cited in each guide, follow the inline links to Cornell LII, CAFC, and the USPTO.