15 U.S.C. § 1666i: Limits on interest rate, fee, and finance charge increases applicable to outstanding balances

In the case of any credit card account under an open end consumer credit plan, no creditor may increase any annual percentage rate, fee, or finance charge applicable to any outstanding balance, except as permitted under subsection (b). prior to commencement of that period, the creditor disclosed to the consumer, in a clear and conspicuous manner, the length of the period and the annual percentage rate that would apply after expiration of the period; the increased annual percentage rate does not exceed the rate disclosed pursuant to subparagraph (A); and the increased annual percentage rate is not applied to transactions that occurred prior to commencement of the period; an increase in a variable annual percentage rate in accordance with a credit card agreement that provides for changes in the rate according to operation of an index that is not under the control of the creditor and is available to the general public; the annual percentage rate, fee, or finance charge applicable to a category of transactions following any such increase does not exceed the rate, fee, or finance charge that applied to that category of transactions prior to commencement of the arrangement; and the creditor has provided the obligor, prior to the commencement of such arrangement, with clear and conspicuous disclosure of the terms of the arrangement (including any increases due to such completion or failure); or include, together with the notice of such increase required under section 1637(i) of this title , a clear and conspicuous written statement of the reason for the increase and that the increase will terminate not later than 6 months after the date on which it is imposed, if the creditor receives the required minimum payments on time from the obligor during that period; and terminate such increase not later than 6 months after the date on which it is imposed, if the creditor receives the required minimum payments on time during that period. The creditor shall not change the terms governing the repayment of any outstanding balance, except that the creditor may provide the obligor with one of the methods described in paragraph (2) of repaying any outstanding balance, or a method that is no less beneficial to the obligor than one of those methods. an amortization period of not less than 5 years, beginning on the effective date of the increase set forth in the notice required under section 1637(i) of this title ; or a required minimum periodic payment that includes a percentage of the outstanding balance that is equal to not more than twice the percentage required before the effective date of the increase set forth in the notice required under section 1637(i) of this title . For purposes of this section, the term “outstanding balance” means the amount owed on a credit card account under an open end consumer credit plan as of the end of the 14th day after the date on which the creditor provides notice of an increase in the annual percentage rate, fee, or finance charge in accordance with section 1637(i) of this title .