Minimum Tick Size Arbitrage
The Formal Definition
A high-frequency trading strategy where wholesale market makers exploit regulatory disparities between lit exchanges (bound by SEC Rule 612 whole-penny tick rules) and off-exchange internalizers (permitted to trade in sub-pennies), capturing retail flow by stepping in front of public limit orders by micro-fractions of a cent.
Spread Capture Advantage = Lit Exchange Minimum Display Increment ($0.0100) - Off-Exchange Internalizer Step-Ahead Price ($0.0001)
Cole Barrett's Reality Check
The Unvarnished Bottom Line"Lit exchanges like the NYSE are locked into penny increments: you can bid $50.00 or $50.01, but you cannot bid $50.0001. Wholesale internalizers don't have that restriction. When a retail order arrives, the internalizer steps ahead of the lit exchange queue by 1/100th of a penny. They jump the line, capture the trade, and collect the spread while public exchange limit orders sit waiting."
Interactive Simulator: Test the Math
Real-World Example: Scenario Breakdown
Examining the real numbers for: Retail customer market buy order for 1,000 shares of stock (Lit NBBO: $20.00 Bid / $20.01 Ask)
| Execution Metric | Resting Public Lit Limit Bid (Rule 612 Compliant) | Off-Exchange Wholesale Internalizer |
|---|---|---|
| Fee / Rate | $1.00 fee | $0.00 internal |
| Spread / Buffer | Rested displayed buy order at $20.00 (Cannot legally quote $20.0001) | Bought incoming retail sell order off-exchange at $20.0001 |
| Execution / Status | Internalizer jumped ahead of lit bid on off-exchange book | Stepped ahead of public lit book by 1/100th of a cent |
| Total Cost / Result | Denied execution priority due to statutory tick rules | Captured sub-penny spread arbitrage without competing on lit bourses |
How Brokers Weaponize This Term
Wholesale market makers lobby against expanding sub-penny quoting to lit public exchanges, preserving off-exchange tick size disparities that allow internalizers to capture non-directed retail order flow.
Broker Evaluation Matrix
Cole Approves
Interactive Brokers: SmartRouting engine routes directly to lit exchanges and midpoint pegged facilities to capture genuine sub-penny price improvement for customers.
Read Audit →Cole Flags / Avoids
PFOF Mobile Brokers: Routes 100% of non-directed retail equity orders to wholesale internalizers that monetize tick-size regulatory arbitrage.
View Trap Details →Frequently Asked Questions
What regulation establishes the US minimum tick size rule?
SEC Regulation NMS Rule 612 (the Sub-Penny Rule) mandates a $0.01 minimum quoting increment on lit exchanges for securities priced at $1.00 or more.
Why did the SEC propose updating the Sub-Penny Rule in recent years?
To allow lit exchanges to quote in half-penny or sub-penny increments on liquid stocks, leveling the playing field between public exchanges and off-exchange wholesale internalizers.