If you pay wages to anyone, the answer is almost always yes: you need a withholding tax number, and in most cases you need two of them. At the federal level that number is an Employer Identification Number (EIN) from the IRS. At the state level it is a separate withholding account issued by the state where your employee works. Whether you actually need either one comes down to what kind of entity you run, whether you have employees, and where those employees are physically located.
Federal EIN: The Triggers That Make One Mandatory
Federal law requires anyone filing a tax return, statement, or other document to include an identifying number assigned by the IRS.1Office of the Law Revision Counsel. 26 USC 6109 – Identifying Numbers For businesses, that number is an EIN, and several situations force you to have one:
- You have employees. The moment you hire your first worker and start paying wages, you need an EIN to withhold and remit federal income tax, Social Security, and Medicare.2Office of the Law Revision Counsel. 26 USC 3402 – Income Tax Collected at Source
- Your business is a corporation or partnership. These entity types need an EIN whether or not they have employees.3Internal Revenue Service. Do You Need a New Employer Identification Number
- You run a multi-member LLC. The IRS treats these as partnerships by default, so they need their own EIN.
- You set up a retirement plan. Opening a 401(k) or other qualified plan requires an EIN even if you had been operating under your Social Security Number.
- You withhold tax on payments to foreign individuals. Paying interest, dividends, or compensation to nonresident aliens triggers withholding and reporting that requires an EIN.4Internal Revenue Service. Publication 515 – Withholding of Tax on Nonresident Aliens and Foreign Entities
Changing your business structure trips people up. Incorporating a sole proprietorship or bringing in partners means you need a new EIN. Simply changing your tax election, such as having an existing LLC taxed as an S corporation, does not; you keep the number you already have.5Internal Revenue Service. When to Get a New EIN The distinction is whether you created a new legal entity or only changed how the IRS classifies an existing one.
When You Can Skip the EIN
Not every business owner needs one. A sole proprietor with no employees, no retirement plan, and no excise tax liability can use a personal Social Security Number for all federal tax purposes. The same goes for a single-member LLC treated as a disregarded entity: with no employees and no excise tax obligations, the owner’s SSN or existing EIN covers all information returns and reporting.6Internal Revenue Service. Single Member Limited Liability Companies
Plenty of sole proprietors get one anyway, mainly to avoid putting a Social Security Number on W-9 forms sent to clients. There is no penalty for having a number you technically don’t need. Just be aware that the IRS limits you to one EIN application per responsible party per day.7Internal Revenue Service. Get an Employer Identification Number
Household Employers Often Miss This
If you pay a nanny, housekeeper, caregiver, or other household worker $3,000 or more in cash wages during 2026, you owe Social Security and Medicare taxes on those wages and need an EIN to report them.8Internal Revenue Service. Household Employer’s Tax Guide You report these taxes on Schedule H attached to your personal Form 1040. You do not need a separate business for the obligation to attach.
Federal income tax withholding from a household employee’s wages is optional. You only withhold it if the employee asks and you agree, in which case they fill out a Form W-4.8Internal Revenue Service. Household Employer’s Tax Guide The Social Security and Medicare piece is not optional once you cross the $3,000 threshold. Many families hiring part-time help don’t realize they’ve become employers in the IRS’s eyes until a notice arrives.
Nonprofits, Estates, and Trusts
Tax-exempt status does not exempt an organization from needing an EIN. The IRS requires every organization applying for or holding tax-exempt status to have one, with or without employees.9Internal Revenue Service. Information for Organizations Applying for Tax-Exempt Status The number appears on the exemption application, every Form 990, and any employment tax return the organization files.
Estates and trusts need their own EINs once they become separate tax entities. When someone dies, the estate cannot continue using the deceased person’s Social Security Number. A personal representative or trustee applies for an EIN to open estate bank accounts, file the estate’s income tax return, and distribute assets. Most irrevocable trusts need one too. A revocable living trust generally does not during the grantor’s lifetime, but will need one after the grantor dies.
State Withholding Accounts Are Separate
Most states impose their own income tax, and if you have an employee working in one of those states, you need a state withholding account number from that state’s revenue agency. This is not your federal EIN; it is a separate account the state uses to track the income tax you withhold from paychecks and, in many cases, your unemployment insurance contributions. Registration is typically free or costs only a few dollars.
The obligation attaches when you establish a connection to the state, usually by having someone perform work inside its borders. Even if your business is headquartered elsewhere, an employee working in another state can trigger a registration requirement there. Remote work has complicated this: an employee who moves may create a new state withholding obligation for you, with no office involved.
Reciprocity Agreements
Some neighboring states have reciprocity agreements that simplify the picture. Under these, an employee who lives in one state but works in another only owes income tax to their home state. The employee files an exemption form with you, and you withhold only for the home state. That can spare you from registering in the work state solely for that employee. Confirm the specific agreement covers your situation before skipping registration.
Not Just Payroll
State withholding obligations extend beyond regular paychecks. Some states require withholding on pension distributions, gambling winnings, and certain payments to independent contractors. Once registered, you file quarterly withholding returns and an annual reconciliation.
What Happens If You Skip Registration
Operating without a required withholding tax number carries real financial consequences. The base federal penalty for failing to comply with identification number requirements is $50 per failure, up to $100,000 per year.10Office of the Law Revision Counsel. 26 USC 6723 – Failure to Comply With Other Information Reporting Requirements
Penalties climb when missing or wrong identification numbers cause information returns to be filed late or incorrectly. For returns due in 2026, the IRS charges $60 per return filed up to 30 days late, $130 if filed between 31 days late and August 1, and $340 if filed after August 1 or not at all. Intentional disregard runs $680 per return with no annual cap.11Internal Revenue Service. Information Return Penalties For a payroll of any real size, those per-return amounts add up quickly.
State consequences vary. They often include interest on tax that should have been withheld, late-registration penalties, and in some states, suspension of business licenses until the account is current.
Once You Know You Need One
The fastest way to get a federal EIN is the IRS online application, which issues the number immediately on approval. The tool runs Monday through Friday from 6:00 a.m. to 1:00 a.m. Eastern, Saturdays from 6:00 a.m. to 9:00 p.m., and Sundays from 6:00 p.m. to midnight.7Internal Revenue Service. Get an Employer Identification Number Paper Form SS-4 by fax takes about four business days; by mail, four to five weeks.12Internal Revenue Service. Instructions for Form SS-4 (12/2025)
Before applying, gather the legal name of the business exactly as it appears on your formation documents, the physical address of the principal location, and the date the business started or was acquired. The IRS also requires a “responsible party,” an individual who controls or manages the entity’s funds, and that person must provide their Social Security Number or Individual Taxpayer Identification Number.13Internal Revenue Service. Form SS-4 – Application for Employer Identification Number
If the responsible party has no SSN or ITIN, common for foreign nationals forming a U.S. entity, they cannot use the online application. Instead they complete Form SS-4 on paper and enter “foreign” on the line asking for the SSN or ITIN. The form can be faxed (about four business days) or mailed (four to five weeks). International applicants can also apply by phone at 267-941-1099 during business hours.12Internal Revenue Service. Instructions for Form SS-4 (12/2025)
State registration works through each state’s department of revenue website. You typically link your federal EIN to a new state withholding account during that registration. Most state portals issue a digital receipt or temporary account number right away, with a physical certificate arriving in two to three weeks. Completing the state step is a prerequisite for legally withholding and remitting state income tax from employee pay.
One last piece once the numbers are in hand: federal law requires you to report each new or rehired employee to your state’s new hire reporting agency within 20 days of their start date, and some states set shorter deadlines.14Administration for Children and Families. New Hire Reporting That obligation applies to every employer with a withholding requirement, not just large companies.