Capital gains tax for married filing separately follows the same 0%, 15%, and 20% long-term structure as any other return, but every income breakpoint that controls those rates is set at exactly half the joint-return amount. The $3,000 capital loss deduction is halved to $1,500. The Net Investment Income Tax kicks in at $125,000 instead of $250,000. Traditional and Roth IRA contributions phase out between $0 and $10,000 of modified AGI, and the student loan interest deduction disappears entirely. Each spouse reports only the sales tied to assets they legally own, on a separate Form 8949 and Schedule D.
The Rate Brackets Are Cut in Half
Long-term gains on assets held more than a year are taxed at 0%, 15%, or 20% based on taxable income. For tax year 2026, the MFS breakpoints are:
- 0% rate: taxable income up to $49,450 (versus $98,900 for joint filers).
- 15% rate: above $49,450 and up to $306,850 (versus $613,700 joint).
- 20% rate: above $306,850 (versus above $613,700 joint).1Internal Revenue Service. Rev. Proc. 2025-32
The compression hurts most when one spouse earns significantly more than the other. On a joint return, the lower earner’s unused room in the 0% band absorbs some of the higher earner’s gains. Filing separately closes that door, so the higher earner reaches the 15% or 20% rate on smaller amounts of gain.
Short-term gains, on assets held a year or less, are taxed at ordinary rates, and those brackets are halved too. The 32% ordinary bracket, for example, starts at $201,775 for MFS filers in 2026 versus $403,550 for joint filers. A large short-term gain can push a separate filer into a higher marginal rate faster than expected.2Internal Revenue Service. Topic No. 409, Capital Gains and Losses
Who Reports Which Sale
Each spouse reports only the transactions tied to assets they legally own. That means a separate Form 8949 listing every sale (date acquired, date sold, proceeds, cost basis) flowing to a separate Schedule D and onto that spouse’s individual Form 1040.3Internal Revenue Service. Instructions for Form 8949 (2025)
Legal title on the brokerage account or deed controls, even if joint funds paid for the asset. Stock held in an account in one spouse’s name belongs on that spouse’s return. Same for inherited property, gifted assets, and anything held in a trust. If both spouses report the same sale, or neither does, IRS matching will flag the return.4Internal Revenue Service. Instructions for Schedule D (Form 1040) (2025)
Community Property States Follow Different Allocation Rules
Title-based allocation applies in separate property states. In the nine community property states (Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin), property acquired by either spouse during the marriage is generally treated as owned equally regardless of whose name is on the account. A gain from selling community property is typically split 50/50 across the two returns, and each spouse attaches Form 8958 to show how the income was divided.5Internal Revenue Service. Publication 555 (12/2024), Community Property
The 50/50 split does not apply to property one spouse can trace back to a separate source, such as an inheritance, a gift from a third party, or an asset owned before the marriage. If separate and community funds were mixed to buy the asset, basis and gain must be allocated proportionally. Detailed records of where the purchase money came from are the only way to avoid the default equal split.
The Capital Loss Deduction Drops to $1,500
When capital losses exceed capital gains, a taxpayer can deduct the excess against ordinary income, capped at $3,000 for joint filers and $1,500 for each MFS spouse. Unused losses carry forward, but the halved deduction means it takes longer to work through them.6Office of the Law Revision Counsel. 26 U.S. Code 1211 – Limitation on Capital Losses
Carryforwards from a prior joint return complicate the switch to separate returns. The carryover belongs to whichever spouse actually realized the loss; it does not get split 50/50 automatically. Each spouse has to trace back through the earlier year’s transactions to determine whose losses generated the carryforward.4Internal Revenue Service. Instructions for Schedule D (Form 1040) (2025)
Selling a Primary Residence
Joint filers can exclude up to $500,000 of gain from the sale of a principal residence. Filing separately drops the maximum to $250,000 per spouse. Each spouse must independently meet the use test (living in the home as a primary residence for at least two of the five years before the sale), and at least one spouse must meet the ownership test.7Office of the Law Revision Counsel. 26 USC 121 – Exclusion of Gain From Sale of Principal Residence
For most couples selling a home with less than $500,000 in gain, this makes no practical difference: two $250,000 exclusions add up. The problem shows up when only one spouse is on the title. If the home is titled to one spouse alone, only that spouse can claim the exclusion on a separate return, capping the household benefit at $250,000. On a joint return, either spouse’s ownership satisfies the requirement for the full $500,000.8Internal Revenue Service. Topic No. 701, Sale of Your Home
Loss Sales Between Spouses Don’t Work
Selling an investment at a loss and having your spouse buy it back within 30 days might look like a way to keep the position while harvesting the loss. It doesn’t work. Section 267 disallows losses on direct or indirect sales between family members, spouses included. The rule applies regardless of filing status, and the disallowed loss vanishes for the selling spouse. The buying spouse can use the disallowed amount to reduce gain when they eventually sell the replacement shares.9Office of the Law Revision Counsel. 26 U.S. Code 267 – Losses, Expenses, and Interest With Respect to Transactions Between Related Taxpayers
Transfers that aren’t structured as open-market sales can still trigger the rule. Courts have treated coordinated broker sales and repurchases across spousal accounts as indirect sales between related parties and disallowed the loss. The safe move: if one spouse sells at a loss, the other should not buy substantially identical stock during the 61-day window around the sale.
Other Investment Limits That Raise the Effective Tax
Net Investment Income Tax
The 3.8% NIIT applies when modified adjusted gross income exceeds a statutory threshold. For MFS filers, that threshold is $125,000, half of the $250,000 joint threshold. These figures are set by statute and do not adjust for inflation, so more filers cross them each year. The tax applies to the lesser of net investment income or the amount by which MAGI exceeds the threshold, and it covers capital gains, dividends, interest, rental income, and royalties.10Internal Revenue Service. Topic No. 559, Net Investment Income Tax
IRA Contributions
An MFS filer covered by a workplace retirement plan faces a phase-out for deducting traditional IRA contributions that runs from $0 to $10,000 of modified AGI. Any MFS filer above $10,000 gets no deduction. Roth IRA contributions face the same $0-to-$10,000 range, so an MFS filer with $10,000 or more in modified AGI cannot contribute to a Roth at all, provided they lived with their spouse at any point during the year. Spouses who lived apart for the entire tax year are treated as single for IRA purposes, which opens up the much higher single-filer phase-out ranges.11Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
Student Loan Interest
MFS filers cannot deduct student loan interest. There is no phase-out; the deduction is simply unavailable. Losing it raises AGI, which can push a filer closer to the NIIT threshold or into a higher ordinary rate on short-term gains.12Internal Revenue Service. Topic No. 456, Student Loan Interest Deduction
Itemizing Consistency
If one MFS spouse itemizes, the other must itemize too, even if the standard deduction would produce a better result. A spouse with minimal itemizable expenses forced into itemizing loses the guaranteed floor of the standard deduction, which can raise taxable income and pull more gain into a taxed bracket.13Internal Revenue Service. Itemized Deductions, Standard Deduction
Switching from Separate to Joint After Filing
Couples who file separately and later realize a joint return would have cost less can amend. The IRS allows a change from MFS to MFJ within three years of the original due date, not counting extensions. The reverse is not true: once a joint return is filed and the deadline (including extensions) has passed, the couple generally cannot switch back to separate returns. That one-way door makes it worth running the numbers both ways before filing, especially in a year with large capital gains.14Internal Revenue Service. 21.6.1 Filing Status and Exemption/Dependent Adjustments