Sources

This page shows how we check the facts on this site, the latest results of those checks, and every source we use. Our sources include federal laws and rules, Medicare.gov pages, guidance and publications from the Centers for Medicare & Medicaid Services (CMS), and CMS data files.

Our list has 277 facts that appear on this site's pages, such as dates, rules and phone numbers. They come from 116 sources. The plan data itself comes straight from CMS's files.

How a Fact Gets on This Site

Each step says whether it runs on its own or is a step we run ourselves.

1. Find the source firstA step we run ourselvesBefore we write a fact, we find where it comes from. That can be a federal rule, a Medicare.gov page, a CMS document or a CMS data file.
2. Tie the sentence to its sourceA step we run ourselvesWe keep a list of the facts this site states, such as dates, rules and phone numbers. Each fact in the list says where it comes from. For some facts (about 3 in 10), the source is our own method or policy.
3. The build check blocks fact-like sentences with no sourceAutomaticIf a sentence matches the patterns our build check looks for (such as dates, rules, deadlines and phone numbers) and isn't tied to the list, the change can't be published.
4. An AI assistant checks new wordingA step we run ourselvesBefore we publish new or changed wording, an AI fact-checking assistant checks each fact against its sources. This is part of our process for wording changes. We run it ourselves. It isn't one of the automatic checks.
5. Every week, a program rereads the web pages we quoteAutomaticEvery week, a program rereads the web pages we quote. It checks that the words we rely on are still there. If they have changed, or a page is gone, it lists the facts that need a new check. Some websites block programs like this. The program reports those pages as not checked, instead of unchanged.
6. Every fact has a next-check dateAutomaticFacts that change every year, such as dates, have a set date. Every fact must be checked again at least once every 400 days. After that date, no update to the site can be published until the fact is checked again.
7. Mistakes are fixed in publicA step we run ourselvesWhen we find a mistake, we fix it on the page. We also list the fix, with its date, on Updates and Corrections.

Proof: The Latest Checks

These are the latest results of our checks. Most link to more detail.

• Every publish: a separate program re-reads CMS's plan files and checks the plan lists, names and costs for every county. On October 26, 2026, it checked 1,029,403 values, and all of them matched. How we check our work
• Medicare Plan Finder: on October 19, 2026, we compared our 2027 plan lists with Medicare Plan Finder in 8 ZIP codes in 7 states. All 492 plans we checked matched: 472 Medicare Advantage plans in all 8 ZIP codes, and 20 stand-alone drug plans in Florida and Minnesota. The ZIP codes we checked
• CMS's state fact sheets: the number of stand-alone drug plans matches in 56 of 56 states and territories. The number of Medicare Advantage plans matches exactly in 47 of 51. In New Jersey, New York, Oregon and Washington, CMS's fact sheet lists 1 to 5 more plans than CMS's plan file, which is the file we use. More about this check
• Our list of facts: every one of the 277 facts on this site names where it comes from. The site can't be published if one doesn't. See all our sources
• Corrections: since October 1, 2026, we have posted 21 corrections to what the site showed. Each one is listed on Updates and Corrections.

One Fact, Start to Finish

Here is one fact from our Common Questions page, and how we keep it true.

What we say

"If your plan is ending, you also have a special window from December 8, 2026 to February 28, 2027."

What the source says

"It begins December 8 of the contract year and ends the last day of the following February."

Source

CMS: 2027 Medicare Advantage and Part D Enrollment Guidance (PDF) (opens in a new tab)

Last checked

October 2026

How it's watched

Every week, our program rereads this source and checks that these words are still there. We must check this fact again by September 2027.

How We Wrote the Common Questions

The questions on our Common Questions page come from what people ask. We read questions people posted on a caregiver forum, news stories about plans ending, the headings of search results, and question pages from other groups, such as KFF. Later, we added questions based on the words people typed into Google when our site showed up in the results.

We drafted the answers with help from an AI assistant. Then each fact in an answer was checked against its sources. Each answer ends with a list of its sources and the month they were last checked.

All Sources

Every source behind a fact on this site, grouped by kind. "Next Check" is when the next fact from that source is due to be checked again.

Found a source that has changed, or a fact that looks wrong? Report a problem. Fixes are listed on Updates and Corrections.