Okla. Stat. tit. 14A, § 14A-2-207: Credit service charge for revolving charge accounts

(1) With respect to a consumer credit sale made pursuant to a

revolving charge account, the parties to the sale may contract for

the payment by the buyer of a credit service charge not exceeding

that permitted in this section.

(2) A charge may be made in each billing cycle which is a

percentage of an amount no greater than

(a) the average daily balance of the account;

(b) the unpaid balance of the account on the same day of

the billing cycle; or

(c) the median amount within a specified range within

which the average daily balance of the account or the

unpaid balance of the account on the same day of the

billing cycle is included. A charge may be made

pursuant to this paragraph only if the seller, subject

to classifications and differentiations he may

reasonably establish, makes the same charge on all

balances within the specified range and if the

percentage when applied to the median amount within

the range does not produce a charge exceeding the

charge resulting from applying that percentage to the

lowest amount within the range by more than eight

percent (8%) of the charge on the median amount.

(3) If the billing cycle is monthly, the charge may not exceed

one and three-fourths percent (1 3/4%). If the billing cycle is not

monthly, the maximum charge is that percentage which bears the same

relation to the applicable monthly percentage as the number of days

in the billing cycle bears to thirty (30). For the purposes of this

section, a variation of not more than four (4) days from month to

month is "the same day of the billing cycle".

(4) Notwithstanding subsection (3), if there is an unpaid

balance on the date as of which the credit service charge is

applied, the seller may contract for and receive a charge not

exceeding fifty cents ($0.50), if the billing cycle is monthly or

longer, or the pro rata part of fifty cents ($0.50) which bears the

same relation to fifty cents ($0.50) as the number of days in the

billing cycle bears to thirty (30), if the billing cycle is shorter

than monthly.