Do I cite the inventor or the company that owns the patent?

The inventor is the author. The assignee is the owner, and assignee records change: US 6,285,999 B1 was assigned to the Leland Stanford Junior University at grant, and its Google Patents record now lists both Google LLC and the Leland Stanford Junior University as current assignees, while the inventor on the front page is still Lawrence Page. Mention the assignee in your text if ownership is part of your argument, and date the statement.

How do I cite a very old patent?

The same way—the front page carries the same elements. Thomas Alva Edison's “Electric lamp”, US 223,898, was filed on 4 November 1879 and granted on 27 January 1880, and both dates are on the document.

Where do I find the official patent document?

Google Patents is the easiest way to search and it reproduces the office front page. For the official record use the issuing office: USPTO (US), the EPO and Espacenet (Europe), WIPO PATENTSCOPE (PCT applications), JPO (Japan). Note that some of these sites are built for browsers and will not respond to scripted requests.

What's the difference between publication number and patent number?

A publication number is assigned when an application is published; the patent number comes with the grant. Kind codes distinguish them—US A1 is a published application, US B1 or B2 a granted patent, EP A1 an application and EP B1 a granted European patent. Cite the granted patent where one exists.

Can I cite a patent that was never granted?

Yes, but label it as an application and give its publication number and kind code. An abandoned or refused application shows what somebody claimed, not what an office allowed, so don't lean on it for a technical claim.

How to Cite a Patent: IEEE Format and What to Include

Patents are primary sources for technical research, prior-art searching and innovation studies. They are also unusually easy to cite accurately, because every element you need is printed on the front page of the document itself.

Why Patent Citation Matters

Patents describe inventions in legally operative language. Citing them precisely establishes prior art, credits inventors correctly, and gives permanent identifiers: a granted patent number never changes, even when the owner does.

Key Information to Gather

From the front page: inventor name(s), the title as granted, the publication number with country and kind code, the issuing office, the filing date, the priority date, and the grant or publication date. Add the URL of the record you used.

Patent number formats by office:

United States: US 6,285,999 B1 (or US6285999B1)
European Patent Office: EP 2 800 811 B1
International (PCT): WO 2013/176772 A1
United Kingdom: GB followed by the national number

The kind-code letter matters. It is how a reader tells a published application from a granted patent.

Quick Reference by Major Style

IEEE — the only one of these four styles that publishes an explicit patent format on a free, current reference guide:

J. K. Author, "Title of patent," U.S. Patent x xxx xxx, Abbrev. Month, day, year.
J. K. Author, "Title of patent," Country Patent xxx, Abbrev. Month, day, year.

One of IEEE's own published examples, which we checked against the patent itself:

W. W. Black and A. Clavin, "Dipole augmented slot radiating element," U.S. Patent 3594806, Jul. 1971.

That patent is real: US 3,594,806, inventors Woodrow W. Black and Alvin Clavin, granted 20 July 1971. (Its front page titles it "Dipole augmented slot radiating elements", in the plural; IEEE prints the singular.)

Note two IEEE habits visible in the format lines: the number is written in spaced groups of three digits rather than with commas, and the month is abbreviated. IEEE also says to "retain or request the day of the month when referencing a patent," and adds: "Use 'issued date' if several dates are given."

One caution about copying examples, including from a style manual. The IEEE Reference Guide also prints J. P. Wilkinson, "Nonlinear resonant circuit devices," U.S. Patent 3 624 125, Jul. 16, 1990. We looked up US 3,624,125: it is "Preparation of aliphatic dinitriles by ammoxidation of hydrocarbons", assigned to Imperial Chemical Industries and granted on 30 November 1971. The number and the title do not belong to the same document, so that entry is a formatting illustration rather than a citable patent. Check every number you copy against the register.

Applied to verified patents:

L. Page, "Method for node ranking in a linked database," U.S. Patent 6 285 999 B1, Sep. 4, 2001.
S. N. Cohen and H. W. Boyer, "Process for producing biologically functional molecular chimeras," U.S. Patent 4 237 224, Dec. 2, 1980.

APA, MLA and Chicago all treat patents as legal or legal-adjacent material, and none of the three publishes a patent example on its free site: APA's patent guidance sits in the legal-references chapter of the Publication Manual, MLA's in the MLA Handbook, and Chicago's Citation Quick Guide has no patent entry. We could not verify a template for them against the style authority or against two independent university library guides, so this page does not present one as official. Check the manual you are required to use, or your library's guide for it.

What all of them need is the same set of elements, and they come off the front page:

[Inventor(s)] · [Year of grant] · [Title as granted] · [Publication number with country and kind code] · [Issuing office] · [URL]

Patent Applications vs. Granted Patents

Granted patents have been examined and allowed. Cite these where they exist — they are the authoritative version of the claims.

Published applications are public but not yet granted, and they may be amended, abandoned or refused. Label them:

[Inventor(s)], "[Title]," PCT Patent Application WO 2013/176772 A1, Nov. 28, 2013.

That publication is real: PCT application WO 2013/176772 A1, "Methods and compositions for RNA-directed target DNA modification and for RNA-directed modulation of transcription", international application PCT/US2013/032589, filed 15 March 2013 with a priority date of 25 May 2012 and published 28 November 2013.

Finding Patent Information

Google Patents: free, searchable, and it reproduces each office's front page, including inventors, assignees at grant and now, and the full date history.
USPTO: the official source for US patents, at uspto.gov.
Espacenet: the EPO's database, covering patents worldwide.
WIPO PATENTSCOPE: international PCT applications.

Wherever you search, read the front page of the document itself before citing. Search-result summaries drop kind codes and abbreviate titles.

Multiple Inventors

Patents often list several inventors, and the order on the front page is the order you use. A verified two-inventor patent, in IEEE form:

S. N. Cohen and H. W. Boyer, "Process for producing biologically functional molecular chimeras," U.S. Patent 4 237 224, Dec. 2, 1980.

IEEE gives a separate "Patent Online" format, which puts the invention first and the URL last — its own basic format reads Name of the invention, by inventor's name. (year, month day). Patent Number [Type of medium]. Available: site/path/file, as in its example Screwless clip mounted computer drive, by D. Williams. (2005, Apr. 26). U.S. Patent 6,885,550 [Online]. Available: http://patft.uspto.gov/netacgi/6,885,550. Applied to the same patent:

Process for producing biologically functional molecular chimeras, by S. N. Cohen and H. W. Boyer. (1980, Dec. 2). U.S. Patent 4,237,224 [Online]. Available: https://patents.google.com/patent/US4237224A/en

And a verified seven-inventor European patent, where the front page lists Martin Jinek, James Harrison Doudna Cate, Wendell Lim, Lei Qi, Emmanuelle Charpentier, Krzysztof Chylinski and Jennifer A. Doudna:

M. Jinek et al., "Methods and compositions for RNA-directed target DNA modification and for RNA-directed modulation of transcription," European Patent EP 2 800 811 B1, May 10, 2017.

Where a list runs long, follow the author-truncation rule of the style you are using rather than trimming it by eye.

International Patents

Use the country or office code and the office's own name. The European patent above is a worked example: application EP 13793997.1, filed 15 March 2013, priority 25 May 2012, granted (B1 publication) 10 May 2017, with the University of Vienna and the University of California among the applicants.

For PCT applications, the issuing body is the World Intellectual Property Organization, and the number takes the WO year/serial form shown above.

Patent Families

One invention usually generates patents in several offices — a patent family. Cite the member you actually read, which is normally the one for the jurisdiction you are writing about.

Where the family itself is the point, name the members individually:

The CRISPR–Cas9 application filed by the University of California and the University of Vienna was published internationally as WO 2013/176772 A1 and granted in Europe as EP 2 800 811 B1.

Citing Specific Claims or Figures

A patent's numbered claims define the legal scope, and its figures are numbered too. Point at them:

In-text: (Page, 2001, claim 1) or (Cohen & Boyer, 1980, Fig. 3)

Claim numbering can change between the application and the grant, so say which document you are reading from.

Assignees vs. Inventors

Inventors are the people named on the front page; they are your authors. Assignees are the entities that hold the rights, and the record changes over time. US 6,285,999 B1 was originally assigned to the Leland Stanford Junior University; its Google Patents record today lists Google LLC and the Leland Stanford Junior University as current assignees.

If ownership matters to your argument, say it in prose, name your source for it and date it:

US 6,285,999 B1 names Lawrence Page as inventor and was assigned at grant to the Leland Stanford Junior University; its Google Patents record lists Google LLC among the current assignees (checked [date]).

Assignment records are maintained by the patent offices — the USPTO's Patent Assignment Search is the authority for US patents — and aggregator pages can lag behind them.

Where These Rules Come From

IEEE: the IEEE Reference Guide, section J ("Patent" and "Patent Online"), published free by the IEEE Author Center. The guide no longer sits at the PDF address most links point to (journals.ieeeauthorcenter.ieee.org/wp-content/uploads/sites/7/IEEE_Reference_Guide.pdf now returns an unrelated page); it is published as a live document linked from the Author Center's "IEEE Editorial Style Manual" page, and that version was read today. The format lines, the Black and Clavin example, the Williams example and the two quoted sentences are taken from it.
APA, MLA, Chicago: patents are covered in the legal-reference chapters of the Publication Manual (7th ed.) and the MLA Handbook (9th ed.), neither of which is reproduced free online, and the free Chicago Manual of Style 18th-edition Citation Quick Guide has no patent entry. We could not verify their patent templates against those authorities or against two independent university library guides, and so do not assert one here.
Every patent on this page was checked today against its Google Patents record, which reproduces the issuing office's front page: US 6,285,999 B1 (inventor Lawrence Page; filed 1998-01-09; published 2001-09-04; original assignee the Leland Stanford Junior University; current assignees listed as Google LLC and the Leland Stanford Junior University); US 4,237,224 (inventors Stanley N. Cohen and Herbert W. Boyer; filed 1979-01-04; published 1980-12-02; priority 1974-11-04); US 223,898 (inventor Thomas Alva Edison; filed 1879-11-04; published 1880-01-27); WO 2013/176772 A1 (PCT/US2013/032589; filed 2013-03-15; priority 2012-05-25; published 2013-11-28; original assignees Universität Wien, University of California Berkeley and University of California San Diego); EP 2 800 811 B1 (application EP 13793997.1; published 2017-05-10; the seven inventors in the order shown above); US 3,594,806 (inventors Woodrow W. Black and Alvin Clavin; published 1971-07-20); US 6,885,550 B1 (inventor Dave Williams; published 2005-04-26); and US 3,624,125, which is not the patent IEEE's Wilkinson example describes.