https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/

PolitiFact is a legalyl registered organization that has a primary purpose of conducting fact-checkings. PolitiFact has been operating continuously since 2007. It is important to note that PolitiFact is owned by the Poynter Institute for Media Studies. IFCN is operated by Poynter.

https://www.politifact.com/truth-o-meter/statements/

PolitiFact conducts regular fact-checks on matters of public concern on a reguarly basis. The fact-checks evaluate distinct claims based on their accuracy. The site publishes several fact-checks per day, usually ranging between 3 and 7 published fact-checks. PolitiFact also publishes stories assessing whether political elites have flip-flopped their position on various political issues. PolitiFact also conducts assessments of how well the President of the United States is delivering on campaign promises.

https://www.politifact.com/truth-o-meter/statements/

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/

PolitiFact conducts fact-checks on a wide variety of political elites from all sides of the political spectrum. My analyses over three randomly sampled months of fact-checks does not find systematic bias in the subjects, speakers, and contexts that get checked. Each fact-check is conducted using the same set of priniciples that are clearly articulated on their website. Moreover, each fact-check is conducted using the same ratings scale (the Truth-O-Meter).

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#Our%20ethics%20policy

PolitiFact does not accept donations from political parties and advocacy organizations. Their website clearly articulates this policy. 

As their site notes, "PolitiFact journalists avoid the public expression of political opinion and public involvement in the political process.

We don’t make political contributions or work on campaigns. We don’t sign online petitions, post yard signs, or participate in political marches.

We avoid expressing political views on social media. We do share news stories and other journalism, but we take care not to be seen as endorsing or opposing a political figure or position. We avoid snarky commentary.

We may participate in the political process as voters, because we also have responsibilities as individual citizens of the United States. But we keep our votes to ourselves as a matter of principle. Our goal is to be open-minded in all of our work." 

The phrase "we don't" is not quite the same thing as "we do not allow," but the policy does appear to meet the spirit of the criterion and the compliance requirements for it.

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#Our%20sourcing

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#Truth-O-Meter%20ratings

PolitiFact is an industry leader on this criterion. Fact-checks provide links to all of the sources PolitiFact journalists use that are publically available (though some have pay walls). They conduct on-the-record interviews. Each story is accompanied by a history of the story (who wrote it, who was interviewed, what documents and the like where used and so forth) which provides as additional layer of transparency for the reader to use when assessing the quality of PolitiFact's work.

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#Our%20funding

https://www.politifact.com/truth-o-meter/blog/2011/oct/06/who-pays-for-politifact/

PolitiFact lists their funders who provide more than 5% of their total revenue, but they do not list how much they get from those funders. PolitiFact also lists the total amount of their individual donations, revealing the names of those who give $1,000 or more. PolitiFact also publishes a link to a modestly redacted version of their 990 disclosure form to allow readers to understand PolitiFact's spending and verify some financial information about PolitiFact.

https://www.politifact.com/truth-o-meter/staff/

All key actors and writers/reporters/editors/correspondents are listed with bio information and contact information. Some, especially at PolitiFact local affiliates are not terribly robust biographies (X is a reporter for PolitiFact...).

https://www.politifact.com/truth-o-meter/staff/

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#How%20to%20contact%20us

Biographies of the director, editors, correspondents, and writers are easy to find on the PolitiFact website. There is also a "how to contact" option, with an email address and a mailing address, that is easy to find. The listing of their staff infludes email addresses and Twitter handles. The how to contact page does not include a relevant Twitter handle or Facebook page to contact, but PolitiFact, again, offers several easy ways for people to get in touch with complaints, suggestions, comments, or reactions. 

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#How%20we%20choose%20claims

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#Our%20sourcing

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#Truth-O-Meter%20ratings

The principles related to how claims are chosen to fact-check, the reporting process and the how the ratings scale of the Truth-O-Meter is operationalied are clearly explained in an acessible place. The different categories of the Truth-O-Meter are generally clear. However, the differences between "half true" and "mostly false" (half true statements are "partially accurate" while a "mostly false" statement "contains  an element of truth" do not have clear distinctions. My hypothesis would be that outside fact-checkers seeking to replicate the work of PolitiFact would come to similar conclusions as PolitiFact, with the caveat that the categories with the lowest correlation to PolitiFact's own work would be half true and mostly false.

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#How%20we%20choose%20claims

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#How%20to%20contact%20us

Our email address is also linked on the pull-down menu under "About Us"--->"Suggest a fact-check"

It is easy for readers to find opportunities to send claims for PolitiFact to fact-check. The website is very clear that every request cannot be honored and that PolitiFact uses a clear set of criteria when deciding what to check (the site lists those criteria plainly for readers).

https://www.politifact.com/truth-o-meter/article/2018/feb/12/principles-truth-o-meter-politifacts-methodology-i/#Correcting%20our%20mistakes

PolitiFact has a detailed corrections policy. For major errors of fact, they make corrections and tag the story - at the top - as corrected. For minor factual errors (that do not change the rating), the correction tag is made at the bottom of the page. Typos and the like are corrected without public notice or fanfare. It is easy for the audience to find the corrections policy and seek corrections. PolitiFact does not tell readers how often they are contacted with corrections requests or what the content and outcomes of those requests were.

https://www.politifact.com/subjects/corrections-and-updates/

PolitiFact meets this criterion. It is easy for readers to see which stories contained corrections and/or updates with substantively meaningful information.