CRA suggests that s. 55(5)(f) designations are unnecessary

CRA stated that its long-standing practice "is to apply subsection 55(2) only to the excess of the taxable dividend paid on a share over the safe income on hand attributable to that share, when issuing an assessment based on subsection 55(2)." Accordingly when a corporate shareholder receives a dividend in excess of SIOH and does not make s. 55(5)(f) designations to carve the dividend up into safe income and taxable dividends, CRA will only apply s. 55(2) to the portion of the dividend in excess of SIOH - so that, by implication, the shareholder is permitted to do the same on a self-assessment basis.

Neal Armstrong. Summary of 16 June 2014 STEP Roundtable Q. 7, 2014-0522991C6 under s. 55(2).