Rule 10b-18

Definition of 'Rule 10b-18'


An SEC rule that provides a "safe harbor" for companies and their affiliated purchasers when the company or affiliates repurchase the company's shares of common stock (i.e., they will not be deemed to have violated anti-fraud provisions of the Securities Exchange Act of 1934). The repurchases must fall within the four conditions of the rule. These cover the manner of purchase, the time of the repurchases, the prices paid and the volume of shares repurchased.

Investopedia explains 'Rule 10b-18'


The rule breaks down as follows:


  • Manner of purchase: The issuer or affiliate must purchase all shares from a single broker or deal during a single day.
  • Timing: An issuer with an average trading volume less than $1 million per day or a public float value below $150 million is unable to trade within the last 30 minutes of trading. Companies with higher average-trading-volume or public float value can trade up until the last 10 minutes.
  • Price: The issuer must repurchase at a price that does not exceed the highest independent bid or the last transaction price quoted.
  • Volume: The issuer can't purchase more than 25% of the average daily volume.


The SEC also specified more detailed disclosure requirements for repurchases. In each quarterly report on Form 10-Q and in the annual report on Form 10-K, the company must provide a table showing, on a month-by-month basis: the total number of shares purchased, the average price paid per share, the total number of shares purchased under publicly announced repurchase programs, and the maximum number of shares that may be repurchased under these programs (or maximum dollar amount if the limit is stated in those terms).



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