SS-4 Lines 16–17: Replace Vague Business Descriptions With Actual Activities

The practical answer

Descriptions such as services, online business, or consulting can hide what a company actually does. A useful activity description names the real product or service and fits the business facts instead of borrowing a broad label from a payment account. Three details shape the review: What product or service is actually provided? Which activity is principal for this application? Do the category and written description agree?^{[1, p.6] [2, p.1]}

Scope and the records behind the answer

The discussion follows the entity, form and transaction conditions identified below. The same label on a different form can have a different purpose. Keep the relevant entity and reporting period visible while you compare the requirements, and treat each stated exception as part of the rule rather than an optional footnote.

Official sources checked: 2026-11-09. Annual tax-year forms and continuously revised forms are identified separately in the references.

A side-by-side preparation table

Work through the official requirements

Activity specific

Choose the single category best describing the principal activity on line 16, then describe that activity more specifically on line 17.^{[1, p.6]}

Field/section 16: Check one box that best describes the principal activity of your business.

Select the single category matching the actual principal activity. If no listed category fits, select Other and explain.^{[2, p.1] [1, p.6]}

Field/section 17: Indicate principal line of merchandise sold, specific construction work done, products produced, or services provided.

Describe the merchandise sold, construction work, products manufactured or services provided specifically, rather than simply repeating a broad category.^{[2, p.1] [1, p.6]}

Authorized signer

The authorized SS-4 signer depends on the type of applicant. A foreign applicant may use a person with appropriate authorization to sign.^{[1, p.6]}

Designee scope

The third-party designee may answer questions about the completed SS-4 and receive the new EIN. Signed authorization is required, and that authority ends when the EIN is assigned and released to the designee.^{[1, p.6]}

Mailing address

Lines 4a-4b identify the mailing address where the entity receives correspondence. A foreign address must include the city, province or state, postal code and full country name.^{[1, p.3]}

Not entity election

Checking an entity-type box on SS-4 is not itself an entity-classification tax election.^{[1, p.4]}

Physical address

Complete lines 5a-5b only when the entity's physical address differs from its mailing address. Do not enter a P.O. box here.^{[1, p.3]}

Default classification

A domestic single-member LLC generally defaults to an entity disregarded as separate from its owner; a domestic LLC with two or more members generally defaults to partnership classification.^{[1, p.3]}

An illustrative preparation scenario

In this hypothetical preparation example, a business profile says online services, while invoices describe design work and a product catalogue describes digital materials. The preparer asks the owner to identify the principal activity, then checks that the category and the written description tell the same story. The preparer checks three points: What product or service is actually provided? Which activity is principal for this application? Do the category and written description agree? The file remains a working comparison until the relevant facts and applicable instructions have been checked together. No agency outcome is assumed.^{[1, p.6] [2, p.1]}

This is a planning illustration, not a statement that a particular filing has been accepted or that an entity qualifies for a tax result. Use the source-backed distinctions above to decide what information still needs to be established before a form is completed.

A review sequence you can actually use

1. What product or service is actually provided?
2. Which activity is principal for this application?
3. Do the category and written description agree?

Write down the answer and the record that supports it, rather than marking a question complete because a field contains text. When two records disagree, identify whether the difference concerns the entity, an individual, the reporting period or the type of change. That makes the remaining question specific enough to resolve against the relevant instruction.

Keep the scope of a preparation service separate from the government requirement. A service intake question may gather information for a workflow; it does not create an exception, extend a deadline or determine whether a transaction is reportable. The cited government material remains the basis for those conclusions.

Questions to settle before moving forward

How should I check field/section 17: indicate principal line of merchandise sold, specific construction work done, products produced, or services provided.?

Describe the merchandise sold, construction work, products manufactured or services provided specifically, rather than simply repeating a broad category. ^{[2, p.1] [1, p.6]}

How should I check authorized signer?

The authorized SS-4 signer depends on the type of applicant. A foreign applicant may use a person with appropriate authorization to sign. ^{[1, p.6]}

How should I check designee scope?

The third-party designee may answer questions about the completed SS-4 and receive the new EIN. Signed authorization is required, and that authority ends when the EIN is assigned and released to the designee. ^{[1, p.6]}

How should I check mailing address?

Lines 4a-4b identify the mailing address where the entity receives correspondence. A foreign address must include the city, province or state, postal code and full country name. ^{[1, p.3]}

Official sources and versions

1. Instructions for Form SS-4 (Rev. December 2025) — Rev. December 2025
2. Form SS-4 (Rev. December 2025) — Rev. December 2025

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