Capital gains taxes for New Mexico investors involve two calculations: federal tax on investment profits and New Mexico income tax after state adjustments. A federal 0% capital gains rate does not automatically make a gain tax free in New Mexico.
The state deduction also changed on January 1, 2025. The old rule allowing a broad 40% deduction no longer applies to ordinary portfolio gains. Using that rule for a stock or fund sale can leave you with an understated state tax bill.
This guide covers investments held in taxable accounts, with federal thresholds for tax year 2026, generally reported on returns filed in 2027. For the wider treatment of investment income, see our guide to investment taxes in New Mexico.
Start With the Gain, Not the Sale Proceeds
A capital gain generally equals the amount realized from a sale minus your adjusted tax basis. Basis often starts with the purchase cost, but adjustments can change it. The cash arriving in your brokerage account is not necessarily the taxable profit.
Suppose you buy shares for $12,000 and later sell them for net proceeds of $18,000. With no basis adjustments, the gain is $6,000, not $18,000. Moving those proceeds into another investment does not, by itself, erase the gain.
The holding period then affects federal treatment. Investments held for more than one year generally produce long-term gains or losses. Holdings sold after one year or less generally produce short-term gains or losses. Net short-term gains face ordinary federal income tax rates, rather than the preferential rates available for most net long-term gains. The IRS capital gains and losses rules cover these distinctions and exceptions.
Before estimating tax, separate purchase cost, sale proceeds, holding period and any adjustments. A portfolio dashboard’s profit figure is useful for monitoring performance, but it should not replace the tax calculation.
Federal Capital Gains Tax Rates for 2026
Most net long-term capital gains fall into federal rates of 0%, 15% or 20%. The thresholds depend on filing status and taxable income, not simply salary, sale proceeds or the size of the gain.
| Filing status | 0% band ends at | 15% band ends at | 20% applies above |
|---|---|---|---|
| Single | $49,450 | $545,500 | $545,500 |
| Married filing jointly | $98,900 | $613,700 | $613,700 |
| Head of household | $66,200 | $579,600 | $579,600 |
| Married filing separately | $49,450 | $306,850 | $306,850 |
These amounts come from the IRS inflation adjustments for 2026 capital gains thresholds. They are not the thresholds for a 2025 return filed during 2026.
Think of preferential gains as sitting above other taxable income. If a single filer has $40,000 of other taxable income and a $20,000 qualifying long-term gain in 2026, $9,450 of that gain fits within the 0% band. The remaining $10,550 falls into the 15% band, producing $1,582.50 of federal capital gains tax in this simplified example.
Crossing a threshold does not make the entire gain taxable at the higher rate. Only the portion crossing into that band receives that rate. Qualified dividends also use preferential rate space, so include them when estimating how much room remains.
The Additional 3.8% Investment Income Tax
Higher-income investors may also owe the federal net investment income tax. It applies at 3.8% to the lesser of net investment income or modified adjusted gross income above the applicable threshold.
The thresholds are $200,000 for single and head-of-household filers, $250,000 for married couples filing jointly, and $125,000 for married people filing separately. A large realized gain can push income over the threshold even when regular earnings do not. The IRS net investment income tax rules explain this separate calculation.
How New Mexico Taxes Capital Gains
New Mexico does not give ordinary investment gains the same separate 0%, 15% and 20% rate schedule used federally. Gains remaining in state taxable income after deductions enter the state’s graduated personal income tax calculation.
The state rate schedule effective January 1, 2025, ranges from 1.5% to 5.9%. Your additional tax depends on where the gain falls within your income brackets. The top rate is not a flat charge on every investor’s profit. The enacted New Mexico income tax rate and capital gains changes establish the revised framework.
Calculate federal and state tax separately before combining them. Applying one percentage to a brokerage profit figure skips the adjustments that can make the two taxable amounts different.
The New Mexico Capital Gains Deduction
For tax years beginning on or after January 1, 2025, the deduction is the greater of:
- Your qualifying net capital gain, capped at $2,500.
- 40% of up to $1 million of net capital gain income from selling a business allocated or apportioned to New Mexico under the applicable state rules.
The business-sale alternative is not a general 40% deduction for stocks, ETFs or mutual funds. Buying shares in a company with New Mexico operations does not establish eligibility for that treatment.
For this deduction, net capital gain means net long-term capital gain exceeding net short-term capital loss. It does not mean every profitable trade. Married taxpayers filing separately who could have filed jointly each receive only half the deduction that would have been allowed on a joint return. The New Mexico PIT-ADJ instructions for the capital gains deduction set out these requirements.
A deduction reduces taxable income, not tax dollar for dollar. Keep that distinction in mind before treating $2,500 as money saved. Our separate guide to New Mexico’s capital gains deduction covers the eligibility and calculation details.
A Worked Federal and State Tax Example
Consider a hypothetical single New Mexico investor selling shares during 2026. Assume:
- The shares produce a $20,000 long-term gain.
- Federal taxable income before the gain is $80,000.
- New Mexico taxable income before this sale is also $80,000, after other adjustments.
- There are no offsetting losses, other capital gains, qualified dividends or business-sale deduction.
- The investor is below the net investment income tax threshold.
Federal calculation: The entire $20,000 gain falls within the 15% band. Federal tax attributable to the gain is $3,000.
New Mexico calculation: The $2,500 deduction leaves $17,500 of additional state taxable income. Both the starting income and resulting income fall within the single filer’s 4.9% state bracket. The additional state tax is $857.50.
Combined result: The estimated additional tax is $3,857.50, or about 19.3% of the gain.
This is an illustration, not a substitute for a return calculation. It holds other deductions and credits constant. Its practical lesson is that a 15% federal rate does not mean a 15% total tax cost, and a state deduction does not reduce the federal gain.
Use Losses and Tax Lots Carefully
Capital losses offset capital gains through the federal netting process. When total capital losses exceed total capital gains, individuals can generally deduct up to $3,000 of the remaining loss against other income each year, or $1,500 if married filing separately. Unused losses generally carry forward.
Loss harvesting means realizing a loss deliberately, often to offset realized gains. Check the wash sale rule before buying a replacement: a loss on stock or securities can be disallowed when substantially identical stock or securities are acquired within 30 days before or after the loss sale. An automatic reinvestment can complicate an otherwise straightforward plan. The IRS investment income publication covers loss carryovers, tax basis and wash sales.
Before selling, compare the tax lots available. Suppose you own two equal-sized share lots: one purchased for $4,000 and another for $7,000. If either lot could be sold for $10,000, the potential gains differ: $6,000 versus $3,000, before adjustments.
Review holding periods alongside those figures. The lot with the smaller gain is not automatically the better choice if its gain receives less favorable treatment. Ask your broker how to identify the intended lot and retain the confirmation. Do not leave that decision to a default setting you have never checked.
Reporting, Records and Multistate Issues
Broker statements are the starting point, not the entire record. Reconcile sale proceeds, basis, acquisition dates and adjustments before preparing the return. Transferred securities and older holdings deserve particular attention because the information available to the current broker may be incomplete.
Keep purchase confirmations, sale confirmations, corporate-action notices, prior loss carryover worksheets and documentation supporting basis changes. Our guide to tax records and reporting for New Mexico traders provides a broader recordkeeping framework.
New Mexico uses PIT-1 for the personal income tax return and PIT-ADJ for state additions, deductions and exemptions. Use the forms for the year being reported, rather than assuming line numbers and instructions remain unchanged.
Moving into or out of New Mexico, selling property in another state, or receiving business-related gains can require allocation or apportionment through PIT-B. A credit for another state’s tax is not automatic and depends on how the income is treated. The New Mexico personal income tax return instructions address filing, allocation and credits for taxes paid to another state.
Plan Payments Before Filing Season
A profitable sale can create a payment obligation before the annual return is due. Do not assume that holding the proceeds until filing season avoids an underpayment penalty.
For federal purposes, common payment benchmarks are 90% of current-year tax or 100% of prior-year tax, subject to payment timing and other requirements. The prior-year benchmark generally rises to 110% when prior-year adjusted gross income exceeds $150,000, or $75,000 for married filing separately.
These are penalty-protection rules, not reductions in the eventual tax bill. Meeting a prior-year benchmark can still leave a balance due. The IRS withholding and estimated tax guidance for 2026 also covers uneven income and the annualized income installment method.
After a large sale, rerun the household tax estimate rather than estimating the gain in isolation. Include other realized gains, available losses, dividends, withholding and estimated payments already made. Check New Mexico payment requirements separately from the federal calculation.
Set aside the expected tax before committing the proceeds elsewhere. For a business sale, rental-property disposal or transaction spanning more than one state, obtain tax advice before signing where possible. There is much more room to make useful decisions before a sale than after the proceeds have arrived.