CRA automatically assigns a corporate income tax account to non-residents who voluntarily register for GST purposes

Where a non-resident which is not carrying on business in Canada (and, therefore, is not subject to any Canadian income tax liability under Part I) voluntarily registers for GST purposes, CRA will automatically assign a corporate tax account irrespective of the non-resident's wishes. In order to be de-registered for income tax purposes, the non-resident must confirm that it has no obligation to file a corporate income tax return, and then close the corporate income tax account by phone or by sending in the right form (an RC 145).

Neal Armstrong. Summary of 2015 CBA Roundtable, Q.26 under ETA s. 240(3)(a).