Master Muir provides a helpful summary of amendment principles in Concord Adex Inc. v. 20/20 Management Limited:
 The law in relation to motions seeking leave to amend a pleading is well settled and was not seriously in dispute on this motion. The applicable principles are summarized in my decision in Greenwald v. Ridgevale Inc., 2016 ONSC 3031 (CanLII), 2016 ONSC 3031 (Master). At paragraph 21 of Greenwald I set out those factors as follows:
• the amendments must not result in prejudice;
• the amendments must be legally tenable;
• the amendments must comply with the rules of pleading;
• a motion to add a party must meet all of the requirements of a motion under Rule 26.01;
• the addition of the party should relate to the same transaction or occurrence;
• the addition of the party should not unduly delay or complicate the hearing;
• the addition of a party will not be permitted if it is shown to be an abuse of process.
It is useful to keep these in mind when considering whether a motion to add a party of the presumptive expiry of the limitation period.
There is also a reminder that standard of discovery applicable when determining whether to add a proposed defendant after the presumptive expiry of the limitation period is reasonable discovery, not possible discovery:
 With respect to all of these arguments it is important to emphasize that it is reasonable discoverability and not the mere possibility of discovery that triggers a limitation period. See Crombie Property Holdings Ltd. v. McColl-Frontenac Inc., 2017 ONCA 16 (CanLII) at paragraph 35; leave to appeal refused, 2017 SCCA No. 85. The proposed defendants appear to be holding the plaintiffs to a standard of perfection. That is simply not the test.