The application of the arm’s length principle is particularly important in connection with the difficult and complex problem of deductions to be allowed to the permanent establishment. It is also generally accepted that in calculating the profits of a permanent establishment, allowance should be made for expenses, wherever incurred, for the purpose of the business of the permanent establishment, including executive and general administrative expenses. Apart from what may be regarded as ordinary expenses, there are some classes of expenditure that give rise to special problems. These include interest and royalties etc. paid by the permanent establishment to its head office in return for money lent or patent rights licensed by the latter to the permanent establishment. They further include commission fees (except for reimbursement of actual expenses) for specific services or for the exercise of management services by the enterprise for the benefit of the establishment. In this case, it is considered that the payments should not be allowed as deductions in computing the profits of the permanent establishment. Conversely, such payments made to a permanent establishment by the head office should be excluded from the profits of the permanent establishment. On the other hand, an allocable share of such payments, e.g., interest and royalties, paid by the enterprise to third parties should be allowed. As noted in paragraph 1 above, this approach is consistent with the approach adopted in interpreting Article 7 in the 2008 OECD Model Convention but it varies from the approach adopted by the OECD in its 2008 Permanent Establishments Report.