At a glance
- "TIN" is the umbrella term. Social Security numbers, EINs, and ITINs are all TINs..
- When a form asks for a "TIN," it wants the number of whoever owns the account: you, your trust, an estate, or a business.
- An "employer" identification number isn't just for employers. Trusts and estates use them too.
- A trust's number can change. A revocable trust usually uses your Social Security number while you are alive, and it needs its own EIN after you die.
- When in doubt, send the form to your attorney or accountant through a secure channel before you sign it.
If tax identification numbers confuse you, you're in good company. The rules are clear enough on paper, but the names are misleading, and the forms don't always help. Even professionals who don't apply for these numbers regularly mix them up.
Take the employer identification number, or EIN. Despite its name, it isn't limited to employers. Your trust may need one even though it has never hired anyone. That's one reason many banks, brokers, and insurance companies ask instead for a "TIN," or taxpayer identification number. They aren't using the wrong term. TIN is the broader one, and it covers whichever number belongs to the account owner.
Let's sort it out.
TIN Is the Umbrella
The IRS needs a way to identify every person and entity it deals with. "Taxpayer Identification Number" is its general term for all of these numbers. The IRS lists five:
- Social Security number (SSN). Issued by the Social Security Administration to individuals.
- Employer identification number (EIN). Used by businesses, estates, and trusts.
- Individual taxpayer identification number (ITIN). For certain people who can't get a Social Security number, such as some nonresident and resident aliens and their spouses and dependents.
- Adoption taxpayer identification number (ATIN). A temporary number for a child being adopted.
- Preparer tax identification number (PTIN). For paid tax return preparers.
For most families, only the first three matter. SSNs and ITINs identify people. EINs identify everything else.
Which Number Goes on the Form?
The best clue is a simple question: who owns the account, asset, or benefit? If you own it, use your number. If your trust owns it, use the trust's number, whatever that is right now.
Which Number Goes on the Form?
| Whose account or asset is it? | Number to use | Keep in mind |
|---|---|---|
| Yours, in your own name | Your SSN | An ITIN if you aren’t eligible for an SSN |
| Your revocable trust, while you are alive | Usually your SSN | The trust is ignored for income tax while you live; no separate return |
| A joint revocable trust, both spouses alive | Usually one spouse’s SSN | Use the number your attorney designated, consistently |
| A joint trust after the first death | Survivor’s share: survivor’s SSN. Family or bypass trust: its own EIN | The split often happens at the first death, not the second |
| A revocable trust after the grantor dies | The trust’s new EIN | Never the decedent’s SSN |
| An irrevocable trust taxed to the grantor, such as many Medicaid asset protection trusts | Often the trust’s EIN; sometimes the grantor’s SSN | Check the certification of trust or ask the drafting attorney |
| Any other irrevocable trust | The trust’s EIN | The trust files its own Form 1041 |
| A probate estate | The estate’s EIN | Separate from any trust’s EIN |
| A business with employees, a partnership, or a corporation | The business’s EIN | One EIN per entity; never shared |
| A sole proprietorship or single-member LLC with no employees | Often the owner’s SSN | Excise taxes, retirement plans, or a bank’s policy may still require an EIN |
A general guide only. The trust document and the way the trust is taxed control, so confirm the number with your attorney or accountant before you sign.
Trusts: The Number Follows the Tax Status
While you are alive, a revocable trust is usually a "grantor trust." For income tax purposes it is ignored: its income is reported on your own return, and it typically uses your Social Security number.
Irrevocable trusts vary. Some are taxed as separate taxpayers and always need their own EIN. Others, including many Medicaid asset protection trusts, are still taxed to the grantor. Those trusts often get an EIN anyway, but the trust's income may still be reported to the grantor. Your certification of trust, or the attorney or accountant who set up the trust, can tell you which number it uses.
When the grantor dies, a revocable trust usually becomes irrevocable and a separate taxpayer, and it needs its own EIN. Getting that application right matters more than most people expect; see our article on getting the trust's EIN right after a death.
Applying for an EIN Without an SSN or ITIN
To apply online, the IRS requires the Social Security number or ITIN of the "responsible party," the person who actually controls the entity (IRS). If the person in control has neither, the choices are:
- Get an ITIN first, then apply online.
- Apply on paper. File Form SS-4 by fax or mail. Keep a copy of the signed Form SS-4. The online tool shows the assignment notice on screen. The fax and mail paths do not, and that copy is what the next institution will ask for.
Don't count on the IRS phone line if you are not an international applicant Phone applications are only for applicants with no legal residence or principal place of business in the United States. A U.S. trustee who has neither an SSN nor an ITIN will be turned away and told to fax or mail Form SS-4.
An attorney or accountant can help as an authorized third-party designee, with your signed authorization. A designee can't stand in as the responsible party, though. That has to be the person who really controls the entity.
SSN or ITIN: What's the Difference?
A Social Security number is tied to work authorization and to Social Security benefits at retirement or disability. An ITIN is only for taxes. It lets someone who can't get a Social Security number, such as a nonresident who owns U.S. property or a business, file returns and pay tax. It does not authorize work or create Social Security benefits.
Still Confused?
Ask before you sign. Your attorney or accountant can usually identify the right number in minutes, and a wrong number on an account application can take months to untangle.
If you're not sure which number a form wants, send it to us before you complete it, with a note about what you're trying to do. Please use a secure portal or encrypted email rather than ordinary email or fax, especially once a Social Security number is on the page. We'll fill in the correct number and send it back.
Bottom Line
"TIN" is the family name; SSN, EIN, and ITIN are its members. Match the number to whoever owns the account, and remember that a trust's number can change with its tax status, most often at a death. When the form and the facts don't line up, a quick question now saves a lot of trouble later.
