Why 855I Applications Get Rejected: 7 Reasons and Fixes

Published October 5, 2026

Under the rejection rule, a CMS-855I is rejected when a fix does not arrive in time after the MAC asks for it: 30 calendar days from the request for missing information, or 30 days from submission for supporting documents. (Source: 42 CFR 424.525, rejection of an enrollment application, (a)(1) and (a)(2).) A rejected application cannot be appealed, and you start again with a new application. (Source: 42 CFR 424.525, rejection of an enrollment application, (c) and (d).)

These seven reasons come straight from the rejection rule and the form. They are in no particular order: CMS does not publish how often each one happens.

1. Your name or business name does not match

The name and SSN in section 2A, and any legal business name and TIN in section 4A, must be the same ones you used to get your NPI, and must match exactly in PECOS and NPPES. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 2.) The form's own tips say to make sure the legal business name in section 4 matches the name on the tax documents. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 2.)

Fix: compare the 855I with your NPPES record and the IRS confirmation letter, character by character. Correct NPPES or the application before you submit.

2. A supporting document is missing

Not furnishing all required supporting documentation within 30 days of submitting is its own rejection reason. (Source: 42 CFR 424.525, rejection of an enrollment application, (a)(2).) Section 12 of the 855I lists them. The ones that apply to most practitioners: (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 12.)

• The CMS-588 Electronic Funds Transfer Authorization Agreement, with a voided check or bank letter. It is not required if you already get paid electronically and your banking is not changing, or if you reassign all of your payments to a group.
• IRS confirmation of your TIN and legal business name, such as a CP-575, when you enroll a professional corporation, professional association or LLC, or enroll as a sole proprietor using an EIN.
• Documentation of any final adverse legal actions.

Fix: go through section 12 line by line and attach every document that applies to you before you submit.

3. The application is unsigned or undated

An unsigned or undated application is listed as a rejection reason. (Source: 42 CFR 424.525, rejection of an enrollment application, (a)(1)(ii).) The certification statement says you must sign and date it to be enrolled. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 15.)

Fix: sign and date section 15, or in PECOS add your electronic or uploaded signature. PECOS will not fully process the application without it. (Source: CMS MLN9658742, Medicare Provider Enrollment (December 2025).)

4. The signature is copied or stamped

An application with a copied or stamped signature is listed as a rejection reason. (Source: 42 CFR 424.525, rejection of an enrollment application, (a)(1)(iii).)

Fix: a real signature from the practitioner, in ink on paper or as an electronic or uploaded signature in PECOS.

5. It was signed too long ago

An application signed more than 120 days before the MAC received it is listed as a rejection reason. (Source: 42 CFR 424.525, rejection of an enrollment application, (a)(1)(iv).)

Fix: if a signed application sat for months, sign and date it again before sending.

6. Someone else signed it

An application signed by a person not authorized to sign is listed as a rejection reason. (Source: 42 CFR 424.525, rejection of an enrollment application, (a)(1)(v).) On the 855I, the practitioner is the only person who can sign, and that authority cannot be delegated. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 15.)

Fix: the practitioner signs personally. An office manager or credentialing staff member cannot sign for them.

7. The wrong form, or the wrong reason for applying

Submitting the incorrect CMS-855 application is listed as a rejection reason. (Source: 42 CFR 424.525, rejection of an enrollment application, (a)(1)(x).) Section 1A of the 855I asks you to check one reason: new enrollee, revalidating, reactivating, reporting a change, and so on. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 1.) Picking the wrong one sends the application down the wrong path. An application that is not needed for the transaction, or a revalidation sent more than 7 months before its due date, is returned rather than processed. (Source: 42 CFR 424.526, return of an enrollment application, (a)(7) and (a)(8).) CMS also says not to submit a revalidation if no due date is listed for you, because the MAC will return it. (Source: CMS MLN9658742, Medicare Provider Enrollment (December 2025).)

Fix: confirm what you are doing before you start. The 855I is for individual physicians and eligible professionals; check the Medicare Revalidation List before revalidating.

When the MAC writes to you

Answer within 30 days, and answer everything in the letter. CMS can extend the period if you are actively working with it to resolve the issues, so if you need longer, say so before the deadline. (Source: 42 CFR 424.525, rejection of an enrollment application, (b).)