"Applicable interest" for a precomputed loan contract means the amount of interest attributable to each monthly installment period. It is computed as if each installment period were one month and any interest charged for extending the first installment period beyond one month is ignored. The applicable interest for any monthly installment period is that portion of the precomputed interest that bears the same ratio to the total precomputed interest as the balances scheduled to be outstanding during that month bear to the sum of all scheduled monthly outstanding balances in the original contract.
"Interest-bearing loan" means a loan in which the debt is expressed as a principal amount plus interest charged on actual unpaid principal balances for the time actually outstanding.
"Precomputed loan" means a loan in which the debt is expressed as the sum of the original principal amount plus interest computed actuarially in advance, assuming all payments will be made when scheduled.
"Substantially equal installment" includes a last regularly scheduled payment that may be less than, but not more than 5% larger than, the previous scheduled payment according to a disclosed payment schedule agreed to by the parties.
205 ILCS 670/15