FDA 510(k) K-Number: How to Decode It, Find It, and Use It for Regulatory Intelligence

What Is a 510(k) K-Number

Every 510(k) submission received by the FDA is assigned a unique identifier called the 510(k) number, commonly known as the K-number. This number is the single most important reference for tracking a premarket notification through the FDA review process and for identifying cleared devices in public databases.

The K-number is assigned when FDA receives the submission — not when the device is cleared. It is included in the Acknowledgment Letter that FDA sends to the submitter upon receipt and processing of the 510(k), and it must be referenced in all subsequent correspondence with FDA regarding that submission.

Important distinction: The Acknowledgment Letter containing the K-number is not a marketing clearance letter. A K-number confirms that FDA received the submission; it does not mean the device has been cleared for marketing.

How the K-Number Format Works

The K-number follows a fixed format: the letter K followed by six digits.

K YY NNNN

Where:

• K — indicates the submission type (all 510(k) premarket notifications start with K)
• YY — the last two digits of the calendar year the submission was received by FDA
• NNNN — a sequential four-digit number assigned in order of receipt within that calendar year, starting at 0001

Examples

The numbering resets to K000001 at the start of each calendar year (note: the year 2000 started at K000001, not K100001 — the format uses two digits for the year).

What the K-Number Tells You Immediately

From a K-number alone, you can determine:

1. When the submission was filed. K25xxxx was filed in 2025. K26xxxx was filed in 2026. This tells you the submission vintage, which is useful for understanding how current the regulatory strategy and testing approach are.

2. Approximate submission volume for the year. If a K-number is K253800, you know FDA received at least 3,800 510(k) submissions in 2025 by the time that submission was filed. This gives you a sense of the overall filing pace.

3. Relative filing sequence. A lower sequence number within the same year means the submission was filed earlier in the year. K260001 was filed in early January; K261500 was filed later, likely around mid-year depending on filing volumes.

How to Find a K-Number

For Your Own Submissions

When you submit a 510(k) via the CDRH Portal, FDA processes the submission and sends an Acknowledgment Letter that includes the assigned K-number. Submissions received before 4 PM ET on a business day are processed the same day.

For Competitor or Predicate Devices

You can find K-numbers for cleared devices through the FDA's publicly searchable 510(k) database. Search by:

• Applicant name (the company that submitted the 510(k))
• Device name (the trade name or generic name)
• K-number (if you already know it and want to look up details)
• Product code (the three-letter FDA product classification code)
• Panel (the advisory panel that reviews the device category)

The database returns records showing the K-number, applicant, device name, date received, decision date, decision (SE or NSE), and product code. For many cleared devices, the database also links to publicly available 510(k) summary documents, statements, and sometimes FOIA-released review memos.

Using the openFDA API

For programmatic access, the openFDA 510(k) endpoint provides JSON-formatted data for all 510(k) records. You can query by K-number, product code, date range, applicant name, or decision code. This is useful for bulk analysis, trend tracking, or integration with regulatory intelligence tools.

How Regulatory Professionals Use K-Numbers

1. Predicate Device Research

When preparing a new 510(k), you must identify predicate devices to demonstrate substantial equivalence. The K-number is your primary reference for citing predicates in your submission.

Your 510(k) application must list the predicate device(s) by their K-number, trade name, and classification. FDA reviewers verify this information in the database, so accuracy is essential.

2. Competitive Intelligence

By tracking K-numbers assigned to competitor companies, you can:

• Identify when competitors filed new 510(k) submissions
• Determine the clearance timeline (date received vs. date of decision)
• Analyze what types of devices are being cleared in your product category
• Monitor new entrants in your device space by tracking unfamiliar applicant names appearing in your product code

For example, if you monitor product code GXT (which covers certain cardiovascular devices) and see a new K-number assigned to a company you do not recognize, that tells you a potential new competitor is seeking clearance in your space.

3. Tracking Submission Progress

After you submit your 510(k), the K-number becomes your reference for all FDA interactions. You will use it to:

• Check submission status through the CDRH Portal
• Reference your submission in pre-submission meetings or follow-up correspondence
• Respond to Additional Information (AI) Requests — the response must include the K-number
• Track amendments and supplements filed to the original submission

4. Regulatory Trend Analysis

Analyzing K-number sequences by year reveals filing trends:

• Total 510(k) submission volumes by year (how active the market is)
• Clearance rates by product code or device panel
• Average review times by comparing date received vs. decision date
• Seasonal patterns (many companies file before fiscal year-end or MDUFA deadlines)

5. Due Diligence for M&A and Licensing

In mergers, acquisitions, or licensing transactions, K-numbers serve as auditable identifiers for a company's cleared device portfolio. During due diligence:

• Verify that claimed clearances actually exist in the FDA database by K-number
• Check whether any K-numbers show NSE (not substantially equivalent) decisions rather than SE (substantially equivalent)
• Identify the age of each clearance to assess whether the regulatory foundation is current or aging
• Map the full product portfolio by pulling all K-numbers associated with the target company

K-Numbers vs. Other FDA Identifiers

The K-number is specific to the 510(k) premarket notification pathway. Other FDA regulatory identifiers serve different purposes:

A single product code (e.g., KRZ for a surgical robot) may have hundreds or thousands of K-numbers associated with different cleared devices in that category. The product code defines the classification; the K-number identifies each individual clearance.

What Happens to Your K-Number After Submission

The lifecycle of a K-number through the FDA process:

1. Submission received — FDA assigns the K-number and sends an Acknowledgment Letter
2. Acceptance review — FDA verifies the submission is complete (eSTAR submissions typically bypass the RTA screening)
3. Substantive review — The lead reviewer evaluates substantial equivalence (target: 90 calendar days)
4. AI Request (if needed) — FDA sends questions; the submitter has 180 days to respond. The K-number is referenced throughout
5. Decision — FDA issues either an SE (Substantially Equivalent) or NSE (Not Substantially Equivalent) letter
6. Public record — If SE, the K-number, device information, and public documents are added to the searchable 510(k) database within 30 days of the decision

If a submission is withdrawn (including if the submitter does not respond to an AI Request within 180 days), the K-number still exists in the system but no clearance is granted. Withdrawn submissions do not appear as cleared devices in the public database.

Supplements and Amendments

After a device is cleared, the original K-number serves as the foundation for subsequent submissions:

• Special 510(k) supplements for design changes reference the original K-number
• Amendments to pending submissions use the same K-number
• Add-to-files and appeals reference the original K-number

This creates a lineage where a single product may have an original K-number plus multiple supplement K-numbers reflecting its regulatory history.

Common Questions About K-Numbers

Can I predict what K-number my submission will receive?

No. K-numbers are assigned sequentially in order of receipt. You cannot request a specific number or predict what number will be assigned.

Does a K-number mean my device is cleared?

No. The K-number is assigned upon receipt, not upon clearance. You receive the K-number in the Acknowledgment Letter before any substantive review has occurred. Only when FDA issues a formal SE letter is the device cleared for marketing.

What if my device receives an NSE decision?

The K-number remains associated with that submission, but the device is not cleared. You would need to submit a new 510(k) (which would receive a new K-number) if you want to pursue clearance. The original NSE K-number is part of the public record.

Can I reference multiple K-numbers for my predicate devices?

Yes. Many 510(k) submissions reference more than one predicate device. You might use one predicate for the overall device concept, another for specific technological features, and a third for certain performance characteristics. All predicates must have the same intended use as your device, and you must address the combined technological characteristics in your substantial equivalence discussion.

Are K-numbers for withdrawn or NSE submissions public?

The 510(k) database primarily shows cleared (SE) devices. NSE and withdrawn submissions are not prominently displayed but may be accessible through FOIA requests or the openFDA API with appropriate filtering.

Sources

• FDA, "510(k) Submission Process" — fda.gov
• FDA, "Premarket Notification 510(k)" — fda.gov
• FDA, 510(k) Premarket Notification Database — accessdata.fda.gov
• FDA, openFDA Device 510(k) API — open.fda.gov
• Greenlight Guru, "FDA 510(k) Database: Overview and How to Access"
• SG Systems, "Using the FDA 510(k) Database for Market Insights"
• Innolitics, "2019 FDA Guidance — Format for Traditional and Abbreviated 510(k)s"