Respecting whether CRA requires every non-resident partner of a US partnership which has been subject to Reg. 105 withholding to file a Canadian tax return to claim a refund of a share of the withholding, CRA stated:
Non-resident partners of a partnership are required to file a Canadian income tax return to calculate their tax liability and to obtain a refund. There is currently no administrative procedure whereby a refund can be issued in respect of a particular non-resident partners share of the Regulation 105 withholding without that partner filing a tax return. However, where a partnership can demonstrate, based on treaty protection, that the normally required withholding is in excess of the ultimate tax liability, the partnership can make an application for a treaty-based waiver of Regulation 105 withholding on behalf of the partners.