1.37 However, there are two particular circumstances in which it may, exceptionally, be both appropriate and legitimate for a tax administration to consider disregarding the structure adopted by a taxpayer in entering into a controlled transaction. The first circumstance arises where the economic substance of a transaction differs from its form. In such a case the tax administration may disregard the parties' characterization of the transaction and re-characterise it in accordance with its substance. An example of this circumstance would be an investment in an associated enterprise in the form of interest-bearing debt when, at arm's length, having regard to the economic circumstances of the borrowing company, the investment would not be expected to be structured in this way. In this case it might be appropriate for a tax administration to characterize the investment in accordance with its economic substance with the result that the loan may be treated as a subscription of capital. The second circumstance arises where, while the form and substance of the transaction are the same, the arrangements made in relation to the transaction, viewed in their totality, differ from those which would have been adopted by independent enterprises behaving in a commercially rational manner and the actual structure practically impedes the tax administration from determining an appropriate transfer price. An example of this circumstance would be a sale under a long-term contract, for a lump sum payment, of unlimited entitlement to the intellectual property rights arising as a result of future research for the term of the contract (as previously indicated in paragraph 1.10). While in this case it may be proper to respect the transaction as a transfer of commercial property, it would nevertheless be appropriate for a tax administration to conform the terms