Do I Need an EIN? A 5-Question Decision Tree for Solo LLC Owners

What an EIN is

Employer Identification Number. A 9-digit tax ID for businesses, like an SSN for a company. Free from the IRS at irs.gov. Issued instantly online during business hours.

The 5-question decision tree

Do you have employees (W-2)? → Yes, you need an EIN.
Are you a multi-member LLC, partnership, or corporation? → Yes, you need an EIN.
Do you have a Solo 401k or SEP-IRA? → Yes, most plan custodians require an EIN.
Does a client or platform require a W-9 with an EIN (not SSN)? → Yes, get one.
Do you want to open a business bank account? → Most banks require one, even for SMLLCs.

If you answered "no" to all five, you technically don't need one. But you probably still should.

Why get one anyway

Reasons it's worth the 10 minutes

Keeps your SSN off W-9s. Clients and platforms see your EIN, not your SSN. Much safer.
Business bank accounts require it. Most banks won't open a business account with just an SSN.
Legitimacy signal. Some clients take "real businesses" more seriously when they have an EIN.
Required for retirement accounts. Solo 401k custodians almost always require an EIN.

The single-member LLC special case

An SMLLC is "disregarded" for federal tax purposes — the IRS treats it like you personally. You can use your SSN on tax forms. But:

You still need an EIN to open a business bank account (almost always)
You need one if you have employees
You need one if you elect S-Corp or C-Corp treatment
You need one for a Solo 401k

In practice, most SMLLCs should get one.

How to get an EIN (10 minutes)

Go to irs.gov/businesses/small-businesses-self-employed/apply-for-an-employer-identification-number-ein-online
Click "Apply Online Now" during business hours (Mon–Fri 7am–10pm Eastern)
Answer ~10 questions about your business structure
At the end, download your EIN confirmation PDF (Form CP 575). Save this forever.

It's free. Anyone charging you for an EIN is scamming you.

When you need a new EIN (vs keeping the old one)

You need a new EIN if:

You incorporate a sole proprietorship
You add partners to a sole proprietorship
A corporation merges or splits
You inherit a business

You keep your existing EIN if:

You change your business name (just update it with IRS)
You change address
You elect S-Corp for an existing LLC
You add or lose employees

Lost your EIN?

Call the IRS Business & Specialty Tax Line: 800-829-4933. They'll give it to you once they verify your identity. Or check your prior-year tax return — it's on Form 1040 if you filed Schedule C or SE.

We flag SMLLC situations where getting an EIN would help.

If your return shows business banking, employees, or retirement contributions without an EIN, we surface the question.