Buying in. The act of purchasing stock to enable the return of stock that has been borrowed.
The term also applies to buying under the rule; see Under the rule.  The term buying in also
applies when property at public vendue (auction) is bought by parties in interest because a high
enough price has not been offered for it.  The term buying in applies when at a foreclosure sale
the property is bought for parties in interest. In the sale at foreclosure of a railroad the road may
be and generally is bought in the interest of its security holders.
On the London Stock Exchange when the seller of a security does not deliver it by the date when it
is due the buyer instructs the official broker to "buy it in"—that is, to make a fresh purchase for
cash by bidding for the security in the market. The difference in price, if any, and the official
broker's commission are paid by the original seller.