A provision in bank loan financing fee letters that permits the agent banks to change the amount, pricing, structure, yield, tenor, conditions, and other terms of the financing if necessary to successfully syndicate the loans. This flexibility is referred to as the "flex language" or "market flex provision."

Flex language may be "closed-ended," meaning that there is a finite list of terms that can be changed if necessary to successfully syndicate the loans. Alternately, it can be "open-ended," meaning that any of the terms of the loan documents may be changed; although agent banks often agree to specific limits on changes to certain terms (such as a cap on increases in the interest rate).

Typical types of "flex" are:

The flex language is included in the fee letter so that it will remain confidential.

Conversely, if a loan is "oversubscribed" because more lenders are willing to commit greater amounts to the loan than the borrower needs, the agent bank may change the terms of the loan to make it more favorable to the borrower in a process that is known as reverse flex. Reverse flex is not documented in the fee letter (or anywhere else) and is an informal arrangement between the borrower and the arrangers.

For changes to flex language resulting from the financial crisis, see Practice Note, Fee Letters Overview: Lending: Flex Language.