As Michelle states, there was a bit of confusion on the part of Medicare itself when the NPI Numbers were first issued. We also had several clients who were bitten by that confusion. They are sole practitioner's and had created corporations through which they did business (which requires a Type 2 NPI Number). We acquired that Type 2 NPI Number as required, and began using it in Box 33a. Whereupon Medicare began rejecting all of our claims. Investigation yielded the answer that the Type 1 Number was supposed to be in Box 33a. So we re-sent the billing, and future billing, with the Type 1 NPI Number in Box 33a. Whereupon Medicare begin rejecting all of these claims. Investigation yielded the contradictory answer that the Type 2 NPI Number was supposed to be in Box 33a. It took us a significant amount of time to get this straightened out - simply because Medicare had to get their message straight internally.
By way of review - here's a bit more detail for others who may be passing by:
NPI Number Type 1 = Who did the work?
NPI Number Type 2 = Who gets paid?
An "organization" is an entity created by the state. It can be a corporation, partnership, LLC, etc. An organization must have a Type 2 NPI Number - to distinguish it from the flesh-and-blood person who owns the organization.
A sole proprietor is an individual provider who has not created a corporation through which to do business. Therefore, a sole proprietor has no need to distinguish the person from the organization that s/he owns, and so needs no Type 2 NPI Number - and in fact may not have one.
Organizations can never "do the work". The work is always done by a flesh-and-blood person.
Organizations can get paid. Just as can flesh-and-blood persons.
An organization can be a billing entity, just as a flesh-and-blood person can be.
So - a Type 1 NPI Number can go in both Box 24J and Box 33a.
A Type 2 NPI Number can only go in Box 33a; never in Box 24J.
ste - if your client created an organization (by filling out paperwork and submitting it to the appropriate authorities), then your client would need to have a Type 2 NPI Number for that organization. If your client has not created an organization, than your client has no situation that requires a Type 2 NPI Number - and in fact may not have one.
Note that the Type 2 NPI Number would be issued to the name of the organization that was included on the application for the Type 2 NPI Number. While mistakes can be made in any bureaucracy, it is not likely that your client would have obtained a Type 2 NPI Number unless they in fact have created an organization - and have place that organization's name on their application for a Type 2 NPI Number.
Finally, a Type 1 NPI Number should never go into Box 33a - unless the billing entity (your client) is truely a sole proprietor and does not own a legal entity (corporation, partnership, LLC, etc.)
See the top of Page 5 at this link:
https://www.cms.gov/Outreach-and-Education/Medicare-Learning-Network-MLN/MLNProducts/Downloads/NPIBooklet.pdf