The U.S. Internal Revenue Service defines a wash sale as "a sale of stock or securities at a loss within 30 days before or after you buy or acquire in a fully taxable trade, or acquire a contract or option to buy, substantially identical stock or securities."   The wash sale period consists of 61 calendar days:  30 days before the sale and 30 days after the sale.   Acquiring the security during this period may disallow an investor from deducting any of the transaction's loss.

The wash sale IRS guidelines are designed to prevent investors from artificially generating losses where they do not actually intend to reduce their holdings in the assets sold.  

Disclaimer:  IB does not provide tax advice. These statements are provided for information purposes only, are not intended to constitute tax advice which may be relied upon to avoid penalties under any international, federal, state, local or other tax statutes or regulations, and do not resolve any tax issues in your favor. We recommend that you consult a qualified tax advisor or refer to the U.S. Internal Revenue Service.