Joint Bank Account Taxes When You’re Not Married

When you share a joint bank account with someone you aren’t married to, the IRS ignores whose name is on the account and looks at whose money is in it. That principle drives every tax question that comes up: joint bank account taxes when you’re not married are calculated by tracing contributions, not by splitting the balance down the middle. Interest is taxed to the person whose deposits earned it. A withdrawal by the non-contributing owner can be a taxable gift from the contributor. And when one owner dies, the entire balance is presumed to belong to the deceased’s estate until the survivor proves otherwise. Married couples get shortcuts around all three of those rules. Unmarried co-owners don’t.

Who Pays Tax on the Interest

The bank reports every dollar of interest on a single Form 1099-INT, tied to the Social Security number of whichever owner is listed first. The IRS then expects each owner to pay tax on the share of interest their own money generated. If you funded 70% of the account and your co-owner funded 30%, the interest income splits 70/30 on your respective returns, regardless of whose SSN the bank used.

The person named on the 1099-INT fixes the mismatch through nominee reporting. You report the full interest amount on Schedule B of your Form 1040, then subtract your co-owner’s share on a line labeled “Nominee Distribution.”¹ You also issue a separate Form 1099-INT to your co-owner showing their portion and send it to the IRS with a Form 1096 transmittal.² Your co-owner then reports that share on their own return.

Skip the nominee step and the IRS’s automated matching system will treat you as if you earned all the interest yourself. If enough tax is left unpaid, the accuracy-related penalty is 20% of the underpayment.³

When a Deposit or Withdrawal Becomes a Gift

Putting money into a joint account isn’t a gift on its own. Under federal regulations, when one person funds a joint bank account and keeps the ability to withdraw the whole balance, no completed gift has happened yet.⁴ The deposit is revocable. The gift is completed later, when the non-contributing owner pulls money out for their own personal use.

How much they withdraw determines what has to be filed. For 2026, you can give up to $19,000 per recipient per year with no gift tax paperwork.⁵ Say your partner withdraws $15,000 from an account you funded and spends it on themselves. No filing is needed. If they withdraw $50,000 for their own new car, you’ve made a completed gift of $50,000, and Form 709 (the federal gift tax return) is required.

Filing Form 709 doesn’t automatically mean writing a check. The first $19,000 is covered by the annual exclusion. The remaining $31,000 counts against your lifetime exemption, which for 2026 is $15 million per individual.⁵ Most people never come close to using that up. But the return itself is mandatory once a gift to any one recipient exceeds the annual exclusion, even when no tax is owed.

Shared Bills Aren’t Gifts

Not every withdrawal by the non-contributing owner counts as a gift. Money spent on shared living costs, like rent both people live in, groceries both people eat, or a utility bill both people use, generally isn’t a gift to the person who pays it. The IRS is looking at withdrawals for the recipient’s sole benefit.

This is where record-keeping earns its keep. If your co-owner pulls $25,000 out and you can’t show what it went to, the IRS can treat the whole thing as a completed gift from you. Keep receipts, and note whether large withdrawals were for a shared purpose or a personal one.

What Happens to the Account When One Owner Dies

Estate tax rules for unmarried joint accounts are harsher than most people expect. The IRS presumes the entire balance belongs to the deceased owner’s estate. The surviving co-owner has to prove, with documentation, how much of the account they funded from their own independent resources. Only what the survivor can trace to their own contributions is excluded from the deceased’s taxable estate.⁶

Compare that to married couples, where only half the account is automatically included in the deceased spouse’s estate no matter who deposited what. For unmarried co-owners, the default is 100% inclusion, and the entire burden of proof sits with the survivor.

Take an account holding $500,000 when one owner dies. If the survivor contributed $150,000 and the deceased contributed $350,000, then $350,000 belongs in the deceased’s gross estate. Without deposit records, the IRS can include the full $500,000. There’s a further trap: money the deceased previously gave to the survivor doesn’t count as the survivor’s own contribution, even if the survivor later deposited it into the joint account.⁶

The 2026 federal estate tax exemption is $15 million per individual, made permanent by the One Big Beautiful Bill Act.⁵ So actual estate tax won’t apply unless the deceased’s total estate exceeds that number. The contribution-tracing rule still matters for large estates, and it can also affect the cost basis the survivor receives in inherited assets.

One more point about access. Joint accounts with a right of survivorship pass automatically to the surviving owner outside probate, so the survivor generally keeps access to the funds. But survivorship only decides who gets the money. It doesn’t change the estate tax inclusion analysis, and the IRS can still count the deceased’s share in the taxable estate even though the money legally belongs to the survivor.

The Records That Decide Every One of These Questions

One theme runs through all of the above: whoever controls the documentation controls the tax outcome. The IRS doesn’t assume a 50/50 split for unmarried joint account holders. It assumes 100% belongs to whichever person is on the hook at the moment. That’s the SSN holder for income tax, the contributor for gift tax, and the deceased for estate tax. It’s on you to prove otherwise.

Records worth keeping from the day you open the account:

Bank statements from your individual account showing the transfers into the joint account, or pay stubs proving deposits came from your earnings.
Receipts, invoices, or written notes for large withdrawals showing whether the money went to a shared expense or a personal one.
A written ownership agreement, signed by both account holders, stating the purpose of the account, each person’s contributions, and each person’s ownership percentage.

The same paper trail does three separate jobs. It supports the interest allocation on your Schedule B nominee reporting. It shows whether a withdrawal was a personal gift or a shared expense for gift tax purposes. And it provides the tracing needed to rebut the 100% estate inclusion presumption when one owner dies.⁶ Building the habit now is far easier than trying to reconstruct years of transactions after a return is questioned or an owner passes away.

A Note on Non-Tax Risks

Taxes aren’t the only exposure. A joint account can be reached by your co-owner’s judgment creditors or, if they owe back taxes, by an IRS levy against the full balance under federal levy authority.⁷ And if either owner receives means-tested benefits like SSI or Medicaid, the entire balance is generally presumed to belong to the benefits recipient unless documented otherwise.⁸ The same contribution records that handle the tax questions are what you’d use to push back in those situations.

1
Internal Revenue Service. Instructions for Schedule B (Form 1040)
2
Internal Revenue Service. Topic No. 403, Interest Received
3
Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty
4
eCFR. 26 CFR 25.2511-1 – Transfers in General
5
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
6
Office of the Law Revision Counsel. 26 USC 2040 – Joint Interests
7
Office of the Law Revision Counsel. 26 USC 6331 – Levy and Distraint
8
Social Security Administration. POMS SI 01140.205 – Joint Checking and Savings Accounts