Section 475(f) Mark-to-Market: The Trader Tax Election Most CPAs Miss

For active traders, the Section 475(f) mark-to-market election is one of the most consequential — and most misunderstood — provisions in the tax code. When properly elected and maintained, it converts trading gains and losses from capital to ordinary, eliminates wash sale rules, lifts the $3,000 net capital loss cap, and opens the door to self-employment retirement plans. When mishandled, it creates phantom income and missed deadlines.

Trader Tax Status: The Prerequisite

Before discussing the 475(f) election, you must qualify as a trader in securities under IRS standards — not an investor. The IRS uses a facts-and-circumstances test, but the relevant factors are well-established:

• Substantial trading activity — typically 720+ trades per year or daily activity.

• Frequent and regular activity, not sporadic.

• Trading is your business, with the intent to profit from short-term price movements rather than long-term appreciation or dividends.

• Substantial time devoted to trading — generally 4+ hours per trading day.

The IRS has successfully challenged trader status in cases where activity was insufficient or where the taxpayer also had significant W-2 income. Documentation matters — trading logs, time records, and a clearly defined business setup all strengthen the position.

What the 475(f) Election Does

Once you qualify as a trader, electing Section 475(f) treats your securities as marked-to-market on the last business day of the year. The mechanics:

• All open positions are deemed sold at fair market value on December 31.

• Resulting gains and losses are ordinary, not capital.

• Wash sale rules under Section 1091 do not apply to securities subject to the election.

• The $3,000 net capital loss limitation does not apply — full ordinary loss treatment is available.

• Trading expenses become fully deductible as Schedule C business expenses (above the line) rather than miscellaneous itemized deductions (which were eliminated for individuals through 2025 anyway).

The Trade-Off

The cost of the election is twofold. First, ordinary income rates (up to 37% federal) replace long-term capital gains rates (up to 23.8% with NIIT). For traders who hold positions long enough to qualify for long-term capital gains, the election is generally unfavorable. Second, SE tax does not apply to trading gains — but it also doesn't apply to losses, meaning Section 199A QBI deduction is generally not available either.

The Critical Deadlines

For an existing taxpayer, the 475(f) election must be filed by the unextended due date of the prior year's return — generally April 15. So electing for tax year 2026 requires filing the election by April 15, 2026. Missing this deadline is fatal — there is no late election relief. The election is filed as a statement attached to the return, and Form 3115 must also be filed in the year of change to convert from cash to mark-to-market accounting.

For a new entity (such as a trader's LLC formed mid-year), the election must be made within 75 days of formation — far more generous than the existing-taxpayer rule.

Entity Structure Matters

Many high-volume traders form a single-member LLC or S-corporation to operate the trading business. The S-corp structure can unlock additional benefits:

• Reasonable W-2 compensation creates earned income for retirement plan contributions.

• Solo 401(k) with up to $70,000 in 2025 contributions ($77,500 with catch-up at 50+).

• SEP-IRA or defined benefit plan for higher-income traders, potentially $200,000+ in annual deferrals.

• Health insurance and other business deductions become available.

Common Mistakes

• Filing the election after the prior-year return deadline (no relief).

• Failing to file Form 3115 in the change year, creating an unauthorized accounting method change.

• Including investment positions (long-term holdings) in the trading account, contaminating the election.

• Failing to segregate investment versus trading accounts on the books.

• Treating the election as one-time when it's actually a permanent change in accounting method that requires IRS consent to revoke.

The Bottom Line

Section 475(f) is a high-stakes election. For the right active trader — particularly those with significant losses or who need ordinary loss treatment — it can be transformative. For others, it forfeits favorable capital gains rates. The decision requires careful modeling of trading patterns, holding periods, and entity structure. Get this wrong and you'll pay the IRS for years.