Independent Personal Services
(1) Subject to the provisions of Article 13, income derived by a resident of a Contracting State in respect of professional services or other activities of an independent character shall be taxable only in that State except in the following circumstances, when such income may also be taxed in the other Contracting State:
- (a) if he has such a fixed base regularly available to him in the other Contracting State for the purpose of performing his activities; in that case, only so much of the income as is attributable to that fixed base may be taxed in that other Contracting State; or
- (b) if his stay in the other Contracting State is for a period or periods amounting to or exceeding in the aggregate 90 days in any 12 month period commencing or ending in the fiscal year concerned; in that case, only so much of the income as is derived from his activities performed in that other State may be taxed in that other State.
(2) The term "professional services" includes especially independent scientific, literary, artistic, educational or teaching activities as well as the independent activities of physicians, lawyers, engineers, architects, dentists and accountants.