PTAN stands for Provider Transaction Access Number. Sometimes the PTAN is also called the provider number, Medicare PIN, or Medicare ID number. The PTAN is not an NPI, Tax ID, or Medicare UPIN.
The PTAN field is only required for Medicare enrollment. If you are trying to submit an enrollment to Medicare you will have to enter your PTAN in the enrollment form or your enrollment will be rejected. If you are a Medicare provider but cannot locate your PTAN reach out to Medicare and request that they provide it for you.
Note: If you're not submitting an enrollment to Medicare and you're still seeing a PTAN field, simply write "N/A" in that field and submit your enrollment.