Most insurance carriers require a W-9 form from both in- and out-of-network healthcare practitioners. But have you ever wondered why it is so integral, not only for reimbursement, but also for credentialing?
A W-9 is a standardized legal document that payers use to collect your EIN or tax ID numbers. Now, here’s a fun fact: it is a fundamental requirement by the Internal Revenue Service (IRS) to ensure tax compliance, but it is never collected by them directly.
Insurance carriers are in charge of collecting Form W-9 from healthcare providers, and then at year-end, they issue a 1099-NEC or 1099-MISC to the IRS to report the practitioner or practice’s income.
This guide will cover everything you need to know about filling out a W-9 form and how it differs from W-8 and 1099, so continue reading!:
When to Use a W-9 Form?
The following are the main use cases of a W-9 form in medical billing:
- The main use of a W-9 is during the credentialing application process. That is, you provide a W-9 to an insurance carrier during the initial contracting phase to link your tax identity to your billing National Provider Identifier (NPI).
- You should also collect a W-9 form from any non-W-2 worker. These include locum tenens physicians, EHR consultants, or freelance medical coders before issuing their first payment.
- Under the One Big Beautiful Bill Act (OBBBA), you must collect a W-9 for any vendor you expect to pay $2,000 or more.
- You must submit a W-9 form to financial institutions when setting up business bank accounts, practice-held investment funds, or merchant services for patient co-pays.
- You are also required to issue an updated W-9 to all active payers and vendors immediately if your practice changes its legal name, office location, or tax classification.
W-9 vs 1099 Form
The key difference is that the contractor (healthcare provider) fills out a W-9 form to provide payment or tax details to the payer. Contrarily, the insurance payer later reports the contractor’s annual earnings on the 1099 form to the IRS.
W-8 vs W-9 Form
The table below offers a glimpse into the key differences between W9 and W8 forms:
| W-8 Form | W-9 Form | |
|---|---|---|
| Who Uses It? | Individuals or entities based outside the US, such as MENA-based partners. | US citizens, green card holders, or US-based companies. |
| Purpose | Its main purpose is to establish foreign status and avoid or reduce the standard 30% US withholding tax. | It is used to provide a TIN so payers can report your income to the IRS without withholding tax. |
| Reporting Form | Results in a 1042-S form if tax was withheld or a treaty was claimed. | Results in a 1099-NEC or 1099-MISC at year-end. |
| Tax ID Required? | Not always, but required if claiming a tax treaty. | Yes (SSN or EIN). |
The main distinction between the two forms lies in who the user is. That is, if the filer is a US citizen or US-based business, a W-9 form applies; otherwise, use a W-8 form.
How to Fill Out a W-9 Form?
The following table discusses the line-by-line guidelines and requirements for filling out the W-9:
| Field Locator | Description | How to Fill It? |
|---|---|---|
| Line 1 | Legal Name | Provide the name exactly as it appears on your individual or business tax return. In case you own a single-member LLC, enter the owner’s name. |
| Line 2 | Business Name | Write your ‘doing business as’ (DBA) or trade name. Leave blank if you operate solely under your personal legal name. |
| Line 3a | Federal Tax Classification | Check any one of the following that best describes you:Individual/sole proprietor: Used by individuals, sole proprietors, or single-member LLCs where the owner is an individual.C corporation: Used by entities legally incorporated as a C corporation.S corporation: Used by entities that have elected S corporation status with the IRS.Partnership: Used by general or limited partnerships.Trust/estate: Used for legal trusts or the estate of a deceased person.LLC: Used by LLCs that are not disregarded entities. Besides, you must enter a letter code in the adjacent box: P (Partnership), C (C corporation), or S (S corporation).Other: Used for specific entities not covered by the above, such as certain non-profits or government organizations. |
| Line 3b | Foreign Interests | You should check this box only if you selected Partnership/Trust/LLC on Line 3a and are providing this form to a partnership, trust, or estate in which you have an ownership interest and any foreign partners. |
| Line 4 | Exemptions | Individuals should leave this blank. This field is usually for specific entities like banks or government agencies. |
| Line 5 | Address | Provide the street address where you want to receive your 1099-MISC or 1099-NEC tax forms. |
| Line 6 | City, State, Zip | Enter the city, state, and zip code corresponding to the address provided in Line 5. |
| Line 7 | Account Numbers | It is an optional field. You can use it if you need to list specific account numbers for the payer’s records. |
| Part I | Tax ID (TIN) | Individuals and sole proprietors should provide their Social Security Number (SSN). Contrarily, entities and corporations should mention their Employer Identification Number (EIN). |
| Part II | Certification | You must sign and date. This certifies that your TIN is correct and you are a US resident. |
Mistakes to Avoid When Using a W-9 Form
Discussed below are some of the common mistakes that providers make while filling out the W-9 form in medical billing:
Mistake #1: Using an Outdated Form
Keep in mind that the IRS recently revised the W-9 form in January 2026.
The new version has Line 3b, i.e., a mandatory checkbox for partnerships and certain LLCs to disclose foreign interests.
Thus, using the older version (2018 or 2024) can result in administrative rejections and delays in provider credentialing.
Mistake #2: The SSN vs. EIN Mix-Up
Many therapists or independent physicians operate as sole proprietors but still use an EIN for medical billing. Here, the issue arises when these providers use the business EIN.
Remember that the IRS wants you to provide your SSN on the W-9 form. In case the name provided on Line 1 does not match the TIN on file, it will trigger a TIN mismatch error. The outcome? It results in a B-Notice to the provider, along with 24% backup withholding.
The First B-Notice
What happens when a name/TIN mismatch occurs for a provider in a 3-year period? The payer must mail the first B-Notice to the provider within 15 business days of receiving the IRS alert.
The healthcare provider must return a new, signed form W-9 with accurate TIN and legal name to stop 24% backup withholding within 30 calendar days.
The Second B-Notice
The payer issues a second B-Notice when a second mismatch for the same provider occurs within 3 calendar years.
At this stage, a standard W-9 form is no longer enough to fix the issue. That is, the healthcare provider must provide official validation within 30 business days:
- For Individuals: A copy of your Social Security Card.
- For Entities: A Letter 147C from the IRS (a formal document confirming your EIN).
When Does the 24% Withholding Apply?
Under IRS Publication 1281, the 24% backup withholding is a mandatory safety net for the IRS. It applies in these four specific scenarios:
- Withholding begins immediately if a provider fails to provide a TIN or submits a wrong TIN.
- If a practice or practitioner fails to resolve a B-Notice (TIN mismatch) within 30 calendar days.
- Leaving the W-9 unsigned or crossing out the backup withholding certification in Part II of the form.
- If the IRS flags a provider for significantly underreporting income on past returns.
Mistake #3: Incorrect LLC Classification
Another common mistake that healthcare providers make is that while filling in Line 3a, they check the box LLC, but forget to write the letter ‘S’ or ‘C’ in the adjacent space.
The Outcome? Without the letter codes, payers may misclassify you and fail to issue a 1099-NEC. In worst-case scenarios, payers can consider you as a partnership, which has different reporting requirements.
Mistake #4: Ignoring the 2026 $2,000 Threshold
For decades, the standard threshold for filing a 1099-NEC was $600. However, under the OBBBA, the threshold for 1099-NEC reporting has jumped to $2,000 for 2026.
Many medical practices believe that if they don’t plan on paying a vendor more than $2,000 this year, they don’t need to bother collecting a W-9 form. Because we are currently in early 2026, many healthcare providers are confused about which number to use:
- For 2025 work (Filing Now): You must still use the $600 threshold.
- For 2026 work (Filing in 2027): You should use the new $2,000 threshold.
Significance of W-9 Form in Medical Billing
Discussed below are the key benefits of a W-9:
Ensures Accurate Payer Credentialing
It helps prevent discrepancies since insurance carriers utilize the W-9 form to verify a healthcare provider’s legal name and TIN. Note that inaccuracies in these details can result in immediate claim denials.
Prevents 24% Backup Withholding
A 24% backup withholding is a requirement that works as a safety net for the IRS, but it can strain the cash flow of your practice. However, a valid, signed W-9 form on file prevents insurance companies from legally withholding this percentage from your gross reimbursements.
Smooth 1099-MISC/NEC Reporting
Did you know that payers use the W-9 data to issue your year-end tax forms? Yes, that is right. Correct data on this form ensures that the income reported to the IRS matches your own records. The result? It minimizes the likelihood of tax audits.
Entity Verification
The W-9 confirms the federal tax classification for healthcare providers structured as LLCs or S-Corps. This ensures insurance payers apply the correct reporting rules to your practice.
Conclusion
With that said, it is time to conclude! We tried to cover every aspect of the W-9 form to help you not only understand how to fill it out, but also to help you gauge why you should ensure accuracy while submitting it.
Hopefully, with this guide as your go-to resource, you will ensure a seamless W-9 submission and prevent B-Notices and 24% backup withholding. However, with so much to handle at your practice, from providing quality care to submitting a W-9, it is understandable if you struggle with billing and coding-related activities.
What do we recommend? You should outsource medical billing services to professionals, like MediBillMD, to unburden your administrative staff.
