PROOF OF FACTS: 26 C.F.R. 301.6109-1(g)(1) status of SSN is recorded in IMF MFR code

By ftsig-admin | October 29, 2025

26 C.F.R. §301.6109-1(g)(1)(i) indicates that an SSN can have either a DOMESTIC or a FOREIGN status at the discretion of the tax return filer:

26 CFR § 301.6109-1 – Identifying numbers.

§ 301.6109-1 Identifying numbers.

(g) Special rules for taxpayer identifying numbers issued to foreign persons—

(1) General rule—

(i) Social security number. 

A social security number is generally identified in the records and database of the Internal Revenue Service as a number belonging to a U.S. citizen or resident alien individual. A person may establish a different status for the number by providing proof of foreign status with the Internal Revenue Service under such procedures as the Internal Revenue Service shall prescribe, including the use of a form as the Internal Revenue Service may specify. Upon accepting an individual as a nonresident alien individual, the Internal Revenue Service will assign this status to the individual’s social security number.

The Mail Filing Requirement (MFR) Code in the IRS Individual Master File (IMF) indicates whether a taxpayer is required to file a specific type of tax return and how the IRS expects to receive it—electronically or by mail.

What Is the MFR Code?

The Mail Filing Requirement (MFR) Code is a one- or two-digit numeric code stored in the Entity section of a taxpayer’s Individual Master File (IMF). It tells the IRS:

  • Whether a taxpayer is required to file a return
  • Which form type is expected (e.g., 1040, 1040-NR)
  • How the return should be filed (mail vs. electronic)
  • Whether the account is active, inactive, or exempt

Common MFR Codes and Their Meanings

Code for the 1040-NR is 09 above.

Codes may vary slightly depending on IRS system updates. Always refer to the latest IRS Document 6209 for authoritative definitions.

Why It Matters

  • Determines IRS expectations: If a return isn’t filed when the MFR code says it should be, the IRS may issue a notice or create a substitute return.
  • Affects compliance checks: MFR codes are used in automated systems to flag non-filers or misfilers.
  • Used in audits and account resolution: IRS agents and tax professionals use MFR codes to verify filing obligations.

The IRS Internal Revenue Manual (IRM) does reference Mail Filing Requirement (MFR) Codes and their meanings, particularly in sections related to taxpayer account management, filing requirements, and transcript analysis. However, the most detailed definitions are still found in IRS Document 6209, Section 8A.

Where MFR Codes Appear in the IRM

The IRM references MFR codes in contexts such as:

  • IRM 3.13.2 – Entity Control Discusses how MFR codes are assigned, updated, and interpreted in the Individual Master File (IMF).
  • IRM 3.13.5 – IMF Account Numbers Covers how MFR codes interact with taxpayer filing status and account setup.
  • IRM 2.3.10 – IDRS Terminal Responses Explains how MFR codes appear in transcript views (e.g., TXMODA, ENMOD).
    https://www.irs.gov/irm/part2/irm_02-003-010
  • IRM 21.2.1 – Filing Requirements Provides guidance on determining whether a taxpayer is required to file and how MFR codes reflect that.
    https://www.irs.gov/irm/part21/irm_21-002-001r

IRM 3.13.2 and IRM 3.13.5 are currently unpublished in the IRS’s online IRM directory. However, they are still active internal manuals and may be accessed through FOIA requests, IRS Disclosure Offices, or by referencing procedural updates in IRS bulletins. We know they are still used because

1. Referenced in Other IRS Manuals and Transcripts

  • Other IRM sections (like IRM 2.3.10 and IRM 21.2.1) explicitly cite IRM 3.13.2 and 3.13.5 as authoritative sources for entity control and filing requirement procedures.
  • IRS training materials and transcript guides often say things like:“Refer to IRM 3.13.2 for MFR code definitions and account setup procedures.”

2. Cited in IRS FOIA Releases and Legal Proceedings

  • FOIA-released documents and court filings involving taxpayer account disputes often include excerpts or references to IRM 3.13.2 and 3.13.5.
  • These citations confirm that IRS agents use these manuals to interpret and manage taxpayer records.

3. Document 6209 Cross-References

  • IRS Document 6209 (the Master File Code reference) frequently says:“See IRM 3.13.2 for additional guidance on MFR codes and filing requirements.”
  • This implies that 6209 is a summary, while 3.13.2 contains operational procedures used by IRS staff.

4. IRS Submission Processing Interim Guidance

  • The IRS maintains an Interim Guidance page for unpublished IRM sections.
  • These updates often say:“This interim guidance supplements IRM 3.13.2 until the next revision is published.”

What You Can Do to Access IRM 3.13.2 and 3.13.5

1. Check the IRS Interim Guidance Page

  • Visit the IRS Submission Processing Interim Guidance page.
  • This page includes procedural updates and interim instructions for IRM Part 3 sections that are not yet published online.
  • While IRM 3.13.2 and 3.13.5 aren’t listed directly, related updates may reference them.

2. Submit a FOIA Request

  • You can formally request unpublished IRM sections via the Freedom of Information Act (FOIA).
  • Specify the IRM section (e.g., “IRM 3.13.2 Entity Control” or “IRM 3.13.5 IMF Account Numbers”) and request the latest version.

3. Contact IRS Disclosure Offices

  • These offices handle public access to internal documents.
  • You can find contact details on the IRS Disclosure Offices page.

4. Use IRS Document 6209 as a Supplement

  • While not a substitute, IRS Document 6209 includes Master File Codes, including MFR codes, which are often referenced in IRM 3.13.2 and 3.13.5.

These sections often refer users to Document 6209 for the full list of codes and their definitions.

What the IRM Says About MFR Codes

  • MFR codes are used to indicate the type of return a taxpayer is expected to file (e.g., 1040, 1040-NR).
  • They help IRS systems determine if a taxpayer is delinquent, exempt, or informational-only.
  • Codes are updated based on taxpayer activity, IRS action, or account merges.

Example from IRM 3.13.2: “The MFR code must be consistent with the taxpayer’s filing requirement. Refer to Document 6209 for valid MFR codes.”

FOOTNOTES:

  1. IRS Document 6209 Download Directory
    https://www.irs.gov/downloads/irs-6209
  2. p. 8A-55: https://www.irs.gov/pub/irs-6209/6209sec8amasterfilecodes.pdf
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