Income in a joint brokerage account is taxed by contribution, not by whose name sits first on the account. Each co-owner owes tax on their share of the dividends, interest, and capital gains, even though the brokerage sends every 1099 to the IRS under a single Social Security number. That gap between what gets reported and what each person actually owes is the source of most confusion around joint brokerage account taxes, and the fix is a process called nominee reporting.
Why the 1099s Only Show One Owner
Brokerages report all income from a joint account under the SSN of the primary account holder, meaning the first person listed on the application. Forms 1099-DIV, 1099-INT, and 1099-B all go to the IRS under that one number no matter who funded the account.1Internal Revenue Service. Publication 550 – Investment Income and Expenses The firm does not track ownership percentages between co-owners.
So the IRS starts with the assumption that the primary holder received 100% of the income. If a co-owner actually funded half, the IRS’s initial picture shows the primary holder earning twice what they truly owe tax on. Closing that gap falls to the account holders.
How Income Gets Split Between Co-Owners
The IRS allocates joint account income by each owner’s actual financial contribution to the account, not by the legal titling.1Internal Revenue Service. Publication 550 – Investment Income and Expenses If you put in 70% of the money and your co-owner put in 30%, that is how dividends, interest, and gains split for income tax. Whether the account is joint tenants with right of survivorship or tenants in common does not change this.
Proof is on you. Keep records of every deposit, transfer, and funding source from the day the account opens. Bank statements showing where the money came from are the simplest documentation. Without them, the IRS may default to treating the primary holder as the sole owner, or push back on any split that is not 50/50.
Nominee Reporting: Moving Income Off Your Return
When your 1099 includes income that belongs to someone else, the IRS treats you as a “nominee.” You are required to issue a separate 1099 to each co-owner reflecting their share and file copies with the IRS.2Internal Revenue Service. General Instructions for Certain Information Returns – Section: Nominee/Middleman Returns That step moves the co-owner’s income onto their return and off yours.
For interest and dividends, you report the full 1099 amount on Schedule B, then subtract the co-owner’s share on a line marked “Nominee Distribution.” The IRS matches that subtraction against the 1099 you filed for the other person.3Internal Revenue Service. Instructions for Schedule B (Form 1040) – Section: Nominees
Capital gains use the same idea with different mechanics. You list the full sale proceeds and cost basis on Form 8949 as reported by the brokerage, enter adjustment code “N” in column (f), and offset the other owner’s share of the gain or loss in column (g). That zeroes out their portion on your return.4Internal Revenue Service. Instructions for Form 8949 Your co-owner then reports their share on their own Form 8949 using the 1099 you sent them.
Skipping this process is not an option. If you leave the numbers as the brokerage reported them, the IRS assumes everything is yours and may send a notice when your return doesn’t match what the co-owner reported on theirs.
Married Couples: When You Can Skip Nominee Reporting
Spouses filing jointly do not need to bother with nominee reporting. All the dividends, interest, and gains land on the same Form 1040 anyway, so it does not matter that the 1099 lists one SSN.
Nominee reporting only comes back into play for married couples filing separately. Then each spouse reports a share based on contributions in a common law state, or based on community property rules if they live in a community property state.
Community Property States
Nine states treat most assets acquired during the marriage as owned equally by both spouses, regardless of who earned the money or whose name is on the account. If you live in one of those states and file separately, you each report half of the community income and file Form 8958 to show how you allocated wages, investment income, and other tax items between the two returns.5Internal Revenue Service. Form 8958, Allocation of Tax Amounts Between Certain Individuals in Community Property States Form 8958 also applies to registered domestic partners in states that recognize them.6Internal Revenue Service. About Form 8958 – Allocation of Tax Amounts Between Certain Individuals in Community Property States Assets one spouse owned before the marriage, or received during the marriage as a gift or inheritance, are generally treated as separate property and reported entirely on that spouse’s return.
Joint Accounts With a Minor: The Kiddie Tax
Opening a joint account with your child creates a wrinkle most parents miss. The child’s share of dividends, interest, and gains is unearned income, and above a certain threshold it gets taxed at the parent’s marginal rate rather than the child’s.
For 2026, the kiddie tax runs in three tiers:7Internal Revenue Service. Topic No. 553, Tax on a Child’s Investment and Other Unearned Income
- First $1,350 is covered by the child’s standard deduction and not taxed.
- The next $1,350 is taxed at the child’s own rate, typically 10% if the child has no other income.
- Anything above $2,700 is taxed at the parent’s marginal rate, which can reach 37%.
The rule applies to children under 19, or under 24 if they are full-time students not providing more than half their own support. A joint account throwing off $5,000 in dividends where the child owns half puts $2,500 on the child, close enough to the threshold that a good year can spill into the parent’s bracket. If you are funding the account mostly yourself, the contribution rule still governs, so the child’s taxable share may be smaller than a straight 50%.
Wash Sales Across Accounts
The wash sale rule catches a lot of joint account holders. Sell a stock at a loss in the joint account and buy the same stock within 30 days in a separate individual account, and the IRS disallows the loss. The rule reaches across all of your accounts, including IRAs and your spouse’s accounts. Brokerages only track wash sales within the same account on the same security, so cross-account wash sales are yours to monitor.
The trap hits active traders hardest. One spouse selling a position at a loss in the joint account while the other buys the same stock in a retirement account creates a wash sale neither brokerage will flag. The disallowed loss adds to the basis of the replacement shares, so it is not gone forever, but the tax benefit is deferred and the recordkeeping gets messy.
Gift Tax When You Fund the Account
Putting money into a joint account can trigger gift tax exposure that is separate from income tax. Whether a gift occurs, and when, depends on how the account is titled.
Tenants in Common
For a tenants in common account, the gift happens the moment you deposit money, because your co-owner has an enforceable right to their share right away. A parent depositing $50,000 into a 50/50 TIC account with an adult child has made a $25,000 gift. With the 2026 annual exclusion at $19,000 per recipient, the $6,000 excess requires filing Form 709, even if the lifetime exemption means no tax is actually owed.
Joint Tenants With Right of Survivorship
JTWROS accounts between non-spouses are more forgiving. Adding a co-tenant does not complete a gift, because the contributing owner can still withdraw the entire balance. The gift completes only when the non-contributing co-owner pulls money out for their own use.8Journal of Accountancy. Creating Joint Ownership: Avoiding the Tax Traps and Other Pitfalls If that withdrawal tops $19,000 in a calendar year, Form 709 is required.
Spouses
Transfers between spouses who are both U.S. citizens qualify for the unlimited marital deduction, so gift tax never enters the picture regardless of amounts. Transfers to a non-citizen spouse instead get a higher annual exclusion ($190,000 for 2025, with the 2026 figure typically inflation-adjusted) in place of the unlimited deduction.
What Happens at Death
The tax treatment when a joint owner dies depends on who the co-owners were and, again, on who contributed what.
Non-Spouse Joint Owners
For a joint account between non-spouses, the IRS presumes the entire account value belongs in the deceased owner’s gross estate. The surviving co-owner can reduce that amount only by proving they contributed their own money.9Office of the Law Revision Counsel. 26 U.S. Code 2040 – Joint Interests Document 40% contribution, and 60% goes in the estate. Without documentation, all of it does. The contribution records that supported your income tax split protect the survivor here too.
Spouses
For a joint account held solely by spouses who are both U.S. citizens, exactly half the account’s value is included in the estate of the first to die, regardless of who contributed.9Office of the Law Revision Counsel. 26 U.S. Code 2040 – Joint Interests That half qualifies for the unlimited marital deduction, which typically eliminates federal estate tax on it.
The Cost Basis Step-Up
Property included in a decedent’s gross estate gets a basis reset to fair market value on the date of death, wiping out unrealized capital gains on the included share.10Office of the Law Revision Counsel. 26 U.S. Code 1014 – Basis of Property Acquired From a Decedent
In a non-spouse JTWROS account funded equally, the decedent’s 50% share steps up. The survivor’s half keeps its original basis. If the account holds stock bought at $40 now worth $100, the surviving owner’s basis on half the shares stays at $40, and the inherited half jumps to $100.
Spouses in common law states get the same treatment on their 50%. Spouses in community property states get more: both halves of community property receive a stepped-up basis when one spouse dies, not just the decedent’s share.10Office of the Law Revision Counsel. 26 U.S. Code 1014 – Basis of Property Acquired From a Decedent On the example above, the surviving spouse’s basis would jump to $100 on every share. For long-held positions with big embedded gains, that double step-up can save tens of thousands in capital gains taxes.
The Net Investment Income Tax
Joint account income can also push a co-owner across the threshold for the 3.8% net investment income tax, which sits on top of regular income tax. It applies when modified adjusted gross income tops $250,000 for joint filers, $200,000 for single filers, or $125,000 for married individuals filing separately.11Internal Revenue Service. Topic No. 559, Net Investment Income Tax Those thresholds do not adjust for inflation, so more taxpayers hit them every year.
If nominee reporting is skipped and the full joint account income lands on the primary holder’s return, a taxpayer already close to the line from salary can cross it on income that was not really theirs. Getting the allocation right is not only about accuracy on paper. It changes total tax owed.