In the context of share issues or offers, the financial institution that agrees to purchase or to procure other institutions (called sub-underwriters) to purchase the shares to the extent that they are not sold under the offer. Most large share issues and offers by listed companies are underwritten.

In the context of a syndicated loan, the lender (usually the arranger) which promises to lend the underwritten sum of money to the borrower, if the loan is not fully subscribed at the end of the syndication period.

In the context of an issue of a debt security, the manager bank which agrees to purchase securities that are not sold to investors, by subscribing for all the securities in the issue and re-selling them.