When spouses file separately but share a brokerage account, each person reports only their own share of the interest, dividends, and capital gains, even though the brokerage sends a single Form 1099 under one Social Security number. For a married filing separately joint investment account, the spouse whose number is on the 1099 reports the full amount and then backs out the other spouse’s portion using nominee adjustments, and the second spouse reports their share on their own return. How you split the income depends on whether you live in a common law or community property state.
How Much of the Income Is Yours
Before touching a form, settle the ownership question. The answer depends on your state.
Common Law States
In common law states, income from an asset belongs to whoever owns the asset. A jointly titled account is presumed owned 50/50, so the income splits evenly. You can argue a different ratio if one spouse contributed more, say from an inheritance, but you need records tracing the funds. Without that documentation, the IRS falls back to an even split.
Community Property States
Nine states follow community property rules: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin. Income earned during the marriage is community property and must be split exactly 50/50 on separate returns, regardless of whose name is on the account.1Internal Revenue Service. Publication 555 – Community Property
Separate property is the exception. Assets owned before marriage or received by gift or inheritance stay separate. Whether the income those assets throw off counts as separate or community depends on the state. Arizona, California, Nevada, New Mexico, and Washington treat income from separate property as separate. Idaho, Louisiana, Texas, and Wisconsin treat it as community income and still require a 50/50 split.1Internal Revenue Service. Publication 555 – Community Property If separate funds are commingled in the joint account, the spouse claiming the income is separate carries the burden of tracing the money back to its original source. No clear paper trail, and the account is treated as community property.
Reporting the Income on Each Return
The brokerage sends the 1099 to whichever spouse’s Social Security number is listed first on the account. That person is the nominee. The IRS matches the 1099 to that spouse’s return, so both returns need to be prepared with the mismatch in mind.
Interest and Dividends on Schedule B
The nominee spouse reports the full amount of interest or dividends from Form 1099-INT or 1099-DIV on their Schedule B, then subtracts the portion belonging to the other spouse on a separate line labeled “Nominee Distribution.” The net figure equals the nominee’s allocated share.2Internal Revenue Service. Publication 550 – Investment Income and Expenses The second spouse reports their allocated portion on their own Schedule B, even though no 1099 arrived in their name.
Married couples catch a break here. The nominee spouse does not have to issue a separate 1099-INT or 1099-DIV to the IRS for the other spouse’s share. That filing requirement applies to unrelated co-owners, not to spouses.2Internal Revenue Service. Publication 550 – Investment Income and Expenses The Schedule B adjustment on each return is enough.
Capital Gains on Schedule D
Capital gains work the same way, with one trap. You must split the proceeds and the cost basis together, in the same proportion. Splitting the gain 50/50 while leaving the full basis on one return will not reconcile. Brokerages report basis on Form 1099-B, so the numbers are there, but each spouse adjusts them to reflect only their share.3FINRA. Cost Basis Basics The nominee reports the full proceeds and basis on Schedule D, then backs out the other spouse’s share on a separate line. The second spouse reports their proceeds and basis on their own Schedule D.
Form 8958 in Community Property States
Community property state filers must attach Form 8958 to each return, showing how every category of income (wages, interest, dividends, capital gains, and more) was allocated between the two spouses.4Internal Revenue Service. About Form 8958 – Allocation of Tax Amounts Between Certain Individuals in Community Property States Both spouses attach their own copy.
Expenses From the Same Account
Allocating income is only half the job. Expenses tied to the account need the same treatment, and MFS status brings its own limits.
Margin interest, if the account carries a balance, is deductible as investment interest expense up to each spouse’s net investment income for the year, with any excess carrying forward.5Office of the Law Revision Counsel. 26 U.S. Code 163 – Interest Allocate it the same way as the income: a 50/50 account produces a 50/50 margin-interest split.
Investment advisory fees and other miscellaneous itemized deductions subject to the 2% AGI floor were suspended by the Tax Cuts and Jobs Act in 2018, and the One Big Beautiful Bill Act made that suspension permanent. These deductions remain unavailable on federal returns for 2026 and later. Some states never adopted the federal suspension, so the allocation can still matter on a state return.
Then there is the itemization trap. If one MFS spouse itemizes, the other must itemize too, even when the standard deduction would be better.6Internal Revenue Service. Other Deduction Questions The MFS standard deduction for 2026 is $16,100.7Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 If one spouse’s deductions exceed that figure and they itemize, the other spouse is locked into itemizing regardless of their own numbers.
MFS Thresholds That Hit Investment Income Harder
Filing separately compresses several thresholds, which can tax the same investment income more heavily than a joint return would.
The 3.8% Net Investment Income Tax kicks in at $125,000 of modified AGI for MFS filers, half the $250,000 joint threshold, and the figure is not indexed for inflation.8Internal Revenue Service. Questions and Answers on the Net Investment Income Tax A couple with $300,000 in combined income might owe no NIIT jointly, yet owe it on both separate returns.
Long-term capital gains brackets for 2026 MFS filers:
- 0% on taxable income up to $49,450
- 15% from $49,451 to $306,850
- 20% above $306,850
The joint 0% bracket runs to roughly double the MFS figure, so a large gain split unevenly between two MFS returns can push one or both spouses into a higher bracket than the couple would face jointly.
Rental losses take the biggest hit. The $25,000 special allowance that lets joint filers deduct rental losses against other income (phased out above $100,000 AGI) drops to zero for MFS spouses who lived together at any time during the year.9Internal Revenue Service. Instructions for Form 8582 Spouses who lived apart the entire year can claim up to $12,500, phasing out between $50,000 and $75,000 of modified AGI.
Trading Between the Two of You
Separate returns do not create separate taxpayers for loss-disallowance purposes. Being married is what triggers the rules below, and filing status changes nothing.
IRS Publication 550 states that if you sell stock and your spouse buys substantially identical stock, you have a wash sale.2Internal Revenue Service. Publication 550 – Investment Income and Expenses A loss sold in your account and bought back by your spouse within 30 days, in any account (joint, separate, even an IRA), is disallowed. The lost deduction gets added to the basis of the replacement shares.
Federal law also bars deducting losses on sales between related parties, and spouses are specifically listed.10Office of the Law Revision Counsel. 26 USC 267 – Losses, Expenses, and Interest With Respect to Transactions Between Related Taxpayers If one spouse sells at a loss and the other buys the same security, even through the same broker, the loss can vanish entirely. Coordinated tax-loss harvesting between spouses is the fastest way to forfeit deductions you thought were safe.
Records That Keep an Audit Short
Nominee adjustments are a known audit trigger because the amount on one spouse’s return will not match the 1099 the IRS has on file. Clean paperwork is the difference between a quick resolution and a drawn-out exchange of letters.
Keep a worksheet showing the original 1099 figures and the allocation formula for each line item, tracing from the 1099 to the amounts on each spouse’s Schedule B or Schedule D. If you are claiming a non-50/50 split in a common law state, hold on to proof of the uneven contribution: bank statements, inheritance records, gift documentation. A written ownership agreement signed before the tax year in question carries more weight than anything drafted after a notice arrives.
Community property filers should keep their Form 8958 and any schedules classifying each income item as community or separate. When separate funds are mixed into a joint account, the tracing records are what stand between you and an IRS determination that all of it is community property subject to the 50/50 rule.