Mandatory Buy-In Notice Discrepancy (FINRA Rule 11810)
The Formal Definition
A formal regulatory close-out procedure under FINRA Rule 11810 where a purchasing broker-dealer issues a mandatory buy-in notice against a selling broker who failed to deliver securities within the settlement cycle, executing an open-market purchase and billing the defaulting seller for the price difference.
Mandatory Buy-In Deficit Liability = (Open Market Buy-In Execution Price - Original Contract Settlement Price) + Administrative Processing Surcharge
Cole Barrett's Reality Check
The Unvarnished Bottom Line"When a short seller fails to deliver stock, they think they can stall forever. FINRA Rule 11810 ends that game. The buying broker issues a Mandatory Buy-In Notice: 'Deliver the shares by 12:00 PM tomorrow, or we will buy them on the open exchange at whatever price the market quotes and send you the bill.' In heavily shorted stocks, buy-in notices trigger explosive short squeezes."
Interactive Simulator: Test the Math
Real-World Example: Scenario Breakdown
Examining the real numbers for: Resolving a 10,000-share settlement failure on an illiquid equity where the short seller failed to deliver shares for 5 business days
| Execution Metric | Securities Lending Sourced Seller | Naked Short Seller under Rule 11810 Buy-In |
|---|---|---|
| Fee / Rate | Standard locate fee | $0 stock commission |
| Spread / Buffer | Secured verified, pre-borrowed shares from an institutional lending desk prior to executing the short sale | Failed to deliver shares; purchasing broker issued a formal FINRA Rule 11810 Mandatory Buy-In Notice |
| Execution / Status | Delivered shares cleanly on T+1; trade cleared through the continuous net settlement system with zero fail notices | Purchasing broker executed an open-market buy-in, purchasing 10,000 shares at the market offer of $35.00 (original sale at $25.00) |
| Total Cost / Result | Clean trade clearance via verified pre-borrow locating | Forced into an emergency open-market buy-in at worst-of-day prices |
How Brokers Weaponize This Term
If you hold heavily shorted shares that have not settled in your account past the T+1 settlement cycle, instruct your broker to issue a formal 'FINRA Rule 11810 Buy-In Notice' to the defaulting seller. This legally compels the clearing firm to buy shares on the open market, resolving your settlement.
Broker Evaluation Matrix
Cole Approves
Interactive Brokers: Operates strict automated locate engines and fully compliant buy-in processing under FINRA Rule 11810, eliminating naked short settlement failures.
Read Audit →Cole Flags / Avoids
Offshore Short Desks: Permits un-located naked short selling, frequently trapping clients in forced open-market buy-in liquidations at peak prices.
View Trap Details →Frequently Asked Questions
How much notice must a broker give before executing a buy-in under Rule 11810?
Under FINRA Rule 11810, the buying broker must provide written notice at least two business days prior to executing the open-market buy-in, giving the defaulting seller time to source the shares.
Can a customer stop a mandatory buy-in notice?
No. If the securities have not been delivered by the deadline specified in the notice, the buying broker is legally obligated to execute the buy-in on the open market.