A specific clause of this act refers directly to APR disclosure on mortgages. It states, if the final annual percentage rate APR is off by more than 0.125% from the initial GFE disclosure, then the lender must re-disclose and wait yet another three business days before closing on the transaction. The calculation for "close-ended credit" (such as a home mortgage or auto loan) can be found here. For a fixed-rate mortgage, the APR is thus equal to its internal rate of return (or yield) under an assumption of zero prepayment and zero default. For an adjustable-rate mortgage the APR will also depend on the particular assumption regarding the prospective trajectory of the index rate. The calculation for "open-ended credit" (such as a credit card, home equity loan or other line of credit) can be found here. In the EU, the focus of APR standardization is heavily on transparency and consumer rights: «a comprehensible set of information to be given to consumers in good time before the contract is concluded and also as part of the credit agreement [...] every creditor has to use this form when marketing a consumer credit in any Member State» so marketing different figures is not allowed. The EU regulations were reinforced with directives 2008/48/EC and 2011/90/EU, fully in force in all member states since 2013. However, in the UK the EU directive has been interpreted as the Representative APR. A single method of calculating the APR was introduced in 1998 (directive 98/7/EC) and is required to be published for the major part of loans. Using the improved notation of directive 2008/48/EC, the basic equation for calculation of APR in the EU is:   In this equation the left side is the present value of the drawdowns made by the lender and the right side is the present value of the repayments made by the borrower. In both cases the present value is defined given the APR as the interest rate. So the present value of the drawdowns is equal to the present value of the repayments, given the APR as the interest rate. Note that neither the amounts nor the periods between transactions are necessarily equal. For the purposes of this calculation, a year is presumed to have 365 days (366 days for leap years), 52 weeks or 12 equal months. As per the standard: "An equal month is presumed to have 30.41666 days (i.e. 365/12) regardless of whether or not it is a leap year." The result is to be expressed to at least one decimal place.