Billing under both tax ID# and SS #

We often run into providers who are having serious issues with their billing that all stem back to billing under a tax ID# or their social security number. Most people think it’s not a big deal, and how messed up can it get. But you would be amazed at how much a provider’s income can be affected by the billing not being submitted correctly regarding the tax ID# or EIN, and the social security number. With NPI numbers now in the picture, the confusion has grown.

It was very common for a provider to have begun their practice years ago and to have started out billing under their social security number. Many did this because it was just easier. They figured they could switch over to a tax ID or EIN number later on, when their practice was bigger. The problem is that switching from a social security number to a tax ID number is not a simple tax.

When a provider changes any information regarding their practice they must notify all insurance carriers using the required method of each insurance carrier. When changing tax ID information, many commercial carriers require that new contracts be signed. Even though the provider may have been in network with an insurance carrier for years, when switching to a tax ID number it is as if it is an entirely new provider. Medicare requires that the appropriate CMS form(s) be completed. In any case, the switch must be reported using the appropriate format.

In addition to switching to a tax ID#, the provider must also obtain a group, or Type II NPI number to correspond with the tax ID number and business name. The provider keeps the individual or Type I NPI to identify themselves as the rendering provider but uses the Type II NPI for billing purposes. An individual or Type I NPI cannot be used with a tax ID# and a legal business name.

When billing they must make sure they have the correct information in the correct locations. For example, the individual NPI must be in the rendering physician box (24J on the CMS form) and the type II or group NPI must be in the provider billing information (33A on the CMS form). The tax ID must be in box 25 on the CMS form with the EIN box checked. But just having the information in the right boxes does not ensure claims will be processed that way. The insurance carriers must also have this information on their provider files this way as well.

We have had many providers who have switched from their social security number to a tax ID number somewhere along the line and cannot figure out why the are not getting payments. Many times when we look into the problem we find that they are billing under their tax ID number but they are enrolled with the insurance carrier under their social security number. When claims are submitted under the tax ID number, they are either processed out of network or denied. So if you have a provider who is receiving a lot of unexplained denials, or claims are being processed out of network when they are participating, you may want to see if they have switched to a tax ID number recently. That may be the whole problem.


2 Responses to “Billing under both tax ID# and SS #”

  1. Barbara Griswold, MFT, author, Navigating the Insurance Maze: The Therapist's Complete Guide to Working With Insurance -- And Whether You Should Says:

    This article makes many good points, but refers frequently to “billing under a tax ID# or their social security number.” This is misleading, since a social secuirity number IS a type of tax ID number. There are two types of tax ID numbers, either can be used on claims — a social security number or an Employer ID number (EIN). Remember that any provider can get an EIN if they don’t want to use their SS number on claims, and they are free and easy to get (go to — don’t fall for one of those con artists offering to get your EIN for you for a fee. Typically you will also need to fill out a W-9 form (you can get this from also) with your new EIN and send it to the plans you work with so they can switch over to your new ID number.
    Hope this helps,
    Barbara Griswold, MFT
    Author, Navigating The Insurance Maze: The Therapist’s Complete Guide to Working With Insurance — And Whether You Should (

    • solutionsmedicalbilling Says:

      Very good point. I don’t always refer to using their ss# as a tax ID#, but you are correct. I put it in the article both ways since some providers don’t know what I mean when I say EIN, or employee Identification number, but I should have clarified that. Thanks for the input! 🙂

      Solutions Medical Billing (

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