Why do I have to get a Social Security Number to file a U.S. income tax return (USCs)?

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U.S. citizens who meet certain income thresholds (currently about US$10,000 for individuals not filing married-jointly; and about US$20,000 for individuals filing married-jointly) who reside outside the U.S. have no choice but to obtain a SSN in order to file tax returns under U.S. law.  See the specific income thresholds for who is required by law to file a U.S. tax return, here.W9 irs form

As explained in a previous post, under U.S. tax jargon a “taxpayer identification number” (TIN) is a broad definition and includes all of the following, which are TINs –

  1. U.S. Social Security Number (“SSN”) in the case of certain individuals (USCs, LPRs and those who have permission to work in the U.S. under a particular visa);
  2. “Individual Taxpayer Identification Numbers” (ITIN) in the case of other individuals who are not USCs or LPRs and not otherwise eligible for a SSN (another post will explain how ITINs are obtained);
  3. Employer identification numbers (EINs) for certain entities, such as corporations, partnerships and trusts.

Most importantly, the regulations specifically require a U.S. citizen to obtain a SSN to use it as the “taxpayer identifying number.”  The relevant regulations provides that

(A) Except as otherwise provided in paragraph (a)(1)(ii)(B) and (D) of this section, and § 301.6109-3, an individual required to furnish a taxpayer identifying number must use a social security number. 

The exceptions referred to above where a SSN is not required in these regulations are principally for individuals who are not U.S. citizens and not eligible to obtain a SSN.  See, Social Security Numbers for Noncitizens as published by the Social Security Administration (“SSA”).  Any U.S. citizen is eligible for obtaining a SSN.  For information regarding applying for a SSN, see the SSA website.Social Security Emblym - SSA

Ironically, it can be very difficult (nearly impossible in some cases) for USCs who have spent most (if not all) of their lives outside the U.S.; considering the methods of proof required by the SSA when the Application For a Social Security Card (Form SS-5-FS) is submitted.

Once a SSN is obtained, the USC is required to complete IRS Form W-9 vis-a-vis third parties providing them proof of their status and SSN.

More will be discussed in later posts about how to get a SSN overseas from a U.S. Embassy and some Consulate offices.  Also, see, The Catch 22 of Opening a Bank Account in Your Own Country – for USCs and LPRs.  

2 thoughts on “Why do I have to get a Social Security Number to file a U.S. income tax return (USCs)?

    Henry said:
    December 3, 2022 at 5:14 am

    This is a great ppost thanks

      International Tax Advisor responded:
      July 16, 2023 at 5:25 pm

      The statutory rules create an obligation for using Social Security Numbers (SSNs); specifically IRC § 6109 and IRC § 6011(b).

      26 U.S. Code § 6109 – Identifying numbers:

      This is the key statutory rule that requires SSNs be used as taxpayer identification numbers. Specifically IRC § 6109(d) says that SSNs must be used – except as otherwise provided: https://www.law.cornell.edu/uscode/text/26/6109

      “(d) Use of social security account number

      The social security account number issued to an individual for purposes of section 205(c)(2)(A) of the Social Security Act shall, except as shall otherwise be specified under regulations of the Secretary, be used as the identifying number for such individual for purposes of this title.”

      The law is clear by statute and states further therein that “For purposes of paragraphs (1), (2), and (3), the identifying number of an individual (or his estate) shall be such individual’s social security account number.”

      IRC 6011(b) grants the Secretary authority to require a method to secure the proper identification of persons who have tax obligations. That subsection reads in its entirety below:

      “(b) Identification of taxpayer

      The Secretary is authorized to require such information with respect to persons subject to the taxes imposed by chapter 21 or chapter 24 as is necessary or helpful in securing proper identification of such persons.”

      You can see some of the bureaucratic details of taxpayer identification numbers and how they are used and collected per this march 2023 report – https://www.irs.gov/pub/irs-pia/irp-pia.pdf

      The IRS Audit Information Management Systems Reference, AIMS-R – explains how –

      “The use of SSN, Name, Address and Federal Tax Information is critical to effectively audit
      tax returns and apply the results of the audit to the correct individual taxpayer. Authority lies
      with IRC 6011, IRC 6109-1, 26 CFR Section 301.6109-1.”


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