Brokerage Commission Structure

A brokerage commission is the fee a broker charges to execute a trade on behalf of a client. Commission structures range from per-share rates (varying by volume tier and asset class) to flat monthly fees to zero-commission models, reflecting the shift from a service economy to automated execution and the fragmentation of the brokerage industry.

The legacy per-share model

For most of the twentieth century, brokers charged a flat rate per share, with discounts for volume. A retail investor executing a 100-share order in General Motors might pay $0.10 per share, or $10 total (roughly equivalent to a 0.2% tax on a $50 stock). Institutional traders facing tighter competition could negotiate rates as low as $0.001 per share for large blocks.

This model aligned incentives poorly: a broker earned the same fee regardless of execution quality, and volume discounts encouraged traders to batch orders inefficiently. It also created an absurd cliff effect—a trader placing an order just above a volume tier would pay dramatically more per share than one placing the next order after hitting the tier threshold.

The per-share model persists in institutional equity trading and options markets but has been largely superseded in retail equity trading.

The rise of flat per-trade commissions

In the 1980s and 1990s, discount brokers began offering flat commissions—often $5–$10 per trade, regardless of order size. This simplified pricing and reduced the advantage of large orders (an institutional trader with a $10 million order still paid the same $10 as a retail trader with a 100-share order). But flat commissions created a new distortion: tiny orders became disproportionately expensive (a $10 commission on a $100 order is a 10% cost), while enormous orders became bargains.

Flat commissions worked well for retail traders making 10–50 trades per month. A trader paying $10 per trade could execute 50 trades per year for $500, a rate that competed with the old per-share model for retail-sized orders. Many brokers bundled flat commissions with education, research, and trading platforms to differentiate from competitors.

Options commissions: a separate, sticky market

Options commissions have remained obstinately high relative to equities. For decades, the standard was $1–$2 per contract, sometimes plus a $0.10 per-contract fee. A trader executing a 10-contract spread—20 legs total—would pay $20–$40 in commissions, easily dwarfing the per-share cost of an equity trade.

Options commissions reflect genuine additional costs: exchanges charge higher fees for options orders, clearing is more complex, and risk management is harder. But the persistence of high commissions also reflects less price competition. Many retail options traders are relatively unsophisticated and do not comparison-shop; many institutional options traders execute through brokers who bundle commissions with prime brokerage services.

Today, some brokers offer per-contract rates as low as $0.50 or even $0.25, and a few charge zero, but the modal retail options commission remains in the $0.65–$1.00 range.

The zero-commission revolution

Beginning around 2015, online brokers realized that commission revenue was declining (due to automation and competition) while customer acquisition costs were rising. Rather than compete on commissions, they reversed course: zero-commission equity trades became the standard at Robinhood, Interactive Brokers, and eventually most major retailers.

This shift was startling to the industry. How could brokers make money? The answer is three-fold:

First, margin interest and lending revenue. A broker that lets a client buy on margin (borrowing cash against securities) charges interest, typically at prime + 1–2%. A client with a $1 million account borrowed 50% will pay $5,000–$10,000 in annual margin interest, far more than commission revenue ever was.

Second, payment for order flow (PFOF). Market makers and payment venues will pay a broker a fraction of a cent per share routed to them, as long as execution quality meets regulatory minimums. A broker executing 10 million shares per month at $0.001 per share generates $10,000 in PFOF revenue—significant if accumulated across millions of retail accounts.

Third, cash drag and other services. A broker holding a client’s idle cash in a low-yield sweep account earns the difference between the broker’s own borrowing rate and what it pays the client. A broker selling premium features (level II quotes, research, options spreads tools) or promoting its own mutual funds generates incremental revenue.

Tiering and volume discounts

Most institutional brokers still use tiered pricing, offering sliding scales based on monthly volume. A client executing 1–100 million shares per month might pay $0.004 per share; one executing 10 billion shares might pay $0.0005. The tier is reset monthly, and crossing the tier boundary can trigger a retroactive credit or charge.

Tiered pricing incentivizes brokers to consolidate volume: a client might choose to send all trades to one broker rather than splitting them across three, to unlock a lower tier rate. This is why large institutions negotiate “bundles” where the broker commits to a fixed monthly volume and rate, simplifying budgeting.

Hidden and indirect costs

Commission is only one component of total trading cost. Many brokers charge separate fees for:

• Market data subscriptions: Professional-grade level II quotes, news feeds, or real-time news can cost hundreds per month.
• Margin interest: Borrowing cash or stock short.
• Options assignment fees: A small charge when an option is exercised.
• Regulatory fees: Pass-through charges for SEC filings or options clearing.
• Wire fees: Moving cash off the platform.

A client comparing two brokers on commission alone might miss that one charges $10/month for data while the other includes it. Over a year, this hidden cost dwarfs the per-trade commission difference.

The impact on trading behavior

Zero-commission trading has democratized market access but also enabled over-trading. A retail trader facing zero commission and retail-sized spreads may trade far more frequently than her economic situation warrants. Historical data suggests commission was a behavioral brake—a trader who paid $10 per trade was more deliberate about entering positions. One paying zero may execute 20 trades per day, incurring substantial market impact and slippage costs that far exceed old-style commissions.

Conversely, zero commissions have eliminated a true friction from small-scale investing. A person investing $1,000 per month in a broad index fund no longer loses 1% of the contribution to commissions.

Fee transparency and regulation

The Securities and Exchange Commission requires brokers to disclose all material fees and charges prominently. Most brokers publish their commission schedules online. However, PFOF is disclosed separately and is opaque to retail clients—a broker receiving $0.005 per share in PFOF on a zero-commission trade is earning money that the client never sees itemized.

Recent regulatory focus has been on whether PFOF creates a conflict of interest: does a broker route orders to a market maker paying the highest PFOF, or to the venue offering the best execution? The Dodd-Frank Act and subsequent SEC rule changes have tightened oversight, but questions remain.

Comparing total cost

A trader choosing a broker should consider total cost, not commission alone:

• Zero-commission equity broker: $0 commission + $5–$10/month in margin interest or data fees + PFOF embedded in wider spreads = total cost 5–15 basis points per trade.
• Flat-rate institutional broker: $5 per trade + tighter execution + no PFOF = total cost 5–10 basis points per trade.
• Per-share tiered broker: $0.0005/share on a 1,000-share order = $0.50 per trade + best-in-class execution + no PFOF = 3–8 basis points.

The choice depends on trade size, frequency, and whether the trader values research and tools.

See also