Dealer in Securities: Definition, Mark-to-Market, and Ordinary Income

A dealer in securities is taxed as a business that holds inventory: every gain or loss from buying and selling is ordinary income, self-employment tax applies to the net earnings, and Section 475 forces mark-to-market accounting on all securities that have not been properly identified as personal investments. That treatment governs dealers automatically, without any election, and it produces a very different result than the capital-gain framework that applies to traders and investors. The federal tax treatment of a dealer in securities is built around one idea repeated across several Code sections: securities in the dealer’s hands are stock in trade, not investment property.

Who Counts as a Dealer

Section 475(c)(1) defines a dealer in securities as a taxpayer who regularly purchases securities from or sells securities to customers in the ordinary course of a trade or business, or who regularly offers to enter into, assume, offset, assign, or otherwise terminate positions in securities with customers in that same business.¹ The controlling word in both prongs is “customers.” A dealer acts as a middleman, providing liquidity and profiting primarily from the spread or markup on transactions rather than from price appreciation on positions held for their own account.

Volume alone does not create dealer status. A small firm that consistently makes markets in a handful of securities qualifies. A high-frequency operator trading only for its own account does not.

Dealer, Trader, or Investor

The three categories occupy separate lanes, and misclassification can shift a tax bill by a wide margin.

A dealer buys from and sells to customers. Securities are inventory. Income is ordinary. Mark-to-market is mandatory. Self-employment tax applies.
A trader buys and sells for their own account to profit from short-term price movements. Gains and losses are capital by default; a trader can elect mark-to-market under Section 475(f). Self-employment tax generally does not apply to trading gains.
An investor holds for appreciation or income. Gains and losses are capital. Business expense deductions are limited. No mark-to-market option exists.

The dealer-trader line is where most confusion arises. Without customers on the other side of the transaction, no level of trading activity converts a trader into a dealer.

Ordinary Income and Ordinary Loss

Section 1221(a)(1) excludes inventory and property held primarily for sale to customers from the definition of a capital asset.² Because a dealer’s securities are inventory, every sale produces ordinary income or ordinary loss, taxed at the graduated rates that apply to any other business.³

The loss side is where the classification becomes powerful. An investor with net capital losses can deduct only $3,000 against other income each year ($1,500 if married filing separately), carrying the rest forward.⁴ A dealer faces no such cap. Ordinary business losses offset other income dollar for dollar, subject only to the excess business loss limitation discussed below.

Mandatory Mark-to-Market

Section 475(a) requires dealers to mark their securities to market. This is automatic. Any security held at the close of the last business day of the tax year is treated as sold for fair market value on that date, and the resulting gain or loss flows into ordinary income for the year.¹ Basis in each security resets to the deemed sale price at the start of the new year.

The effect is that a dealer cannot defer tax by holding appreciated inventory. Every position is revalued annually, and the tax bill tracks the economic performance of the book in real time. For securities traded on an established exchange, closing price supplies fair market value. For illiquid positions the statute does not prescribe a method and instead grants regulatory authority to Treasury, so dealers typically rely on pricing models, comparable transactions, or independent appraisals, and should document the methodology carefully.⁵ IRS examiners scrutinize this area.

Segregating Personal Investments

Not everything a dealer owns has to go through mark-to-market. Section 475(b)(1) exempts three categories: securities held for investment, certain debt instruments acquired in the ordinary course of business and not held for sale, and securities that hedge non-dealer positions.⁵

The identification requirement is strict. The dealer must clearly identify each exempt security in their records before the close of the day it was acquired, and the identification must specify which exemption applies.⁶ Miss the same-day deadline and the security defaults into the mark-to-market pool, taxed as inventory regardless of the dealer’s actual intent. Any dealer running a personal portfolio alongside the business needs internal procedures that catch every acquisition on the day it happens.

Self-Employment Tax

Dealer income comes from an active trade or business, so it generally triggers self-employment tax at a combined rate of 15.3%: 12.4% for Social Security and 2.9% for Medicare.⁷ The Social Security portion applies only to net earnings up to $184,500 in 2026.⁸ Medicare has no cap.

An additional 0.9% Medicare surtax applies to self-employment earnings above $200,000 for single filers and $250,000 for joint filers. Half of the total self-employment tax is deductible as an adjustment to income, which softens the effect but does not close the gap between a dealer’s effective rate and the long-term capital gain rate an investor would pay on comparable economic returns.

The Net Investment Income Tax Question

The 3.8% net investment income tax under Section 1411 applies to individuals with modified adjusted gross income above $200,000 ($250,000 joint). The statute reaches income from passive activities and from any “trade or business of trading in financial instruments or commodities,” while excluding income from other active trades or businesses.⁹ The second prong is broad enough that a dealing operation may be swept in even when the dealer actively participates. Congress directed Treasury to issue regulations preventing overlap between self-employment tax and NIIT on the same income, but the interaction is complex, and the answer for any given dealer depends on entity structure and the nature of the business.

Wash Sale Exemption

The wash sale rule under Section 1091 disallows a loss when an investor or trader sells a security and buys a substantially identical one within 30 days on either side of the sale. Dealers get an explicit statutory exemption: the disallowance does not apply when the taxpayer is a dealer in stock or securities and the loss arises in a transaction made in the ordinary course of that business.¹⁰ A dealer providing continuous liquidity will inevitably sell and reacquire the same securities repeatedly, and the exemption accommodates that reality. Securities the dealer has segregated as personal investments remain subject to the standard wash sale rules.

What Happens in a Loss Year

Ordinary loss treatment is generous, but two limitations shape how quickly a dealer can actually use the losses.

First, the excess business loss rule under Section 461(l) applies to sole proprietors, partners, and S corporation shareholders. For 2026, non-corporate taxpayers cannot use more than $313,000 in business losses ($626,000 for joint filers) to offset non-business income such as investment returns, interest, or wages from another job. Anything above the threshold is converted into a net operating loss and carried forward.

Second, a net operating loss arising after 2017 can offset only 80% of taxable income in any carryforward year.¹¹ The remaining 20% is always taxed. Together, these rules mean a catastrophic year cannot be absorbed all at once; the tax benefit is spread across future returns.

No Election Required

Dealers do not file an election to obtain any of this treatment. Section 475(a) applies automatically the moment the taxpayer meets the statutory definition. The Section 475(f) election is a separate mechanism aimed at traders who want to opt into mark-to-market and ordinary treatment voluntarily; it does not apply to dealers and is not something a dealer needs to consider. What a dealer does need is careful documentation of same-day identifications for any securities intended to fall outside inventory treatment, and a defensible valuation methodology for any positions that are not priced by an active market.

1
Office of the Law Revision Counsel. 26 U.S.C. 475 – Mark to Market Accounting Method for Dealers in Securities
2
Office of the Law Revision Counsel. 26 U.S.C. 1221 – Capital Asset Defined
3
Internal Revenue Service. Federal Income Tax Rates and Brackets
4
Internal Revenue Service. Topic No. 409, Capital Gains and Losses
5
Office of the Law Revision Counsel. 26 U.S. Code 475 – Mark to Market Accounting Method for Dealers in Securities
6
eCFR. 26 CFR 1.475(b)-2 – Exemptions, Identification Requirements
7
Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)
8
Social Security Administration. Contribution and Benefit Base
9
Office of the Law Revision Counsel. 26 U.S.C. 1411 – Imposition of Tax
10
Office of the Law Revision Counsel. 26 U.S. Code 1091 – Loss From Wash Sales of Stock or Securities
11
Office of the Law Revision Counsel. 26 U.S.C. 172 – Net Operating Loss Deduction