Article 56 EC must be interpreted as meaning that, in the case of rules of a Member State which provide that, where interest applied to the part of an overall debt categorised as excessive has been paid by a resident company to a lending company established in a non-member country with which the borrowing company has special relations, it is not deductible as an expense for the purposes of determining taxable profit, but where such interest is paid to a resident lending company with which the borrowing company has special relations, it is deductible for those purposes, those rules are precluded where, if the lending company established in a non-member country does not have a shareholding in the resident borrowing company, they nevertheless presume that the overall debt owed by the borrowing company forms part of an arrangement designed to avoid the tax normally payable or where they do not make it possible, at the outset, to determine their scope with sufficient precision.