CRA indicates that a GST/HST election to render memberships taxable is inferred if GST/HST is charged

Sched. V, Pt. VI, ss. 18 and 17 describe a GST/HST exemption for a supply of a membership in a professional organization or a public sector body in qualifying circumstances – unless an election is made (on Form GST 124 or GST23, respectively) for s. 18 or 17 to not apply to the supply. CRA stated:

In general, the CRA would accept that an election was made under section 17 or 18 even though the organization did not complete the required form, if the organization has always acted as though it had made the election in question.

Unsurprisingly, CRA stated that a fresh election is not required for each membership supply, and explained that the signed election is regarded as having a continuing effect respecting all future supplies until the election is revoked by completing Part D of the form.

Neal Armstrong. Summary of 28 February 2019 CBA Roundtable, Q.2 under ETA Sched. V, Pt. VI, s. 17.