Source: http://isthatlegal.ca/index.php?name=478-case-law
Timestamp: 2019-04-21 18:31:18+00:00

Document:
On motion at any stage of an action the court shall grant leave to amend a pleading on such terms as are just, unless prejudice would result that could not be compensated for by costs or an adjournment.
The rule requires the court to grant leave to amend unless the responding party would suffer non-compensable prejudice; the amended pleadings are scandalous, frivolous, vexatious or an abuse of the court’s process; or the pleading discloses no reasonable cause of action: Iroquois Falls Power Corp. v. Jacob Canada Inc., 2009 ONCA 517 (CanLII), 75 C.C.L.I. (4th) 1, at paras. 15-16, leave to appeal to SCC refused, 2010 CarswellOnt 425, and Andersen Consulting v. Canada (Attorney General) (2001), 2001 CanLII 8587 (ON CA), 150 O.A.C. 177 (C.A.), at para. 37.
The amendment may be permitted at any stage of the action: Whiten v. Pilot Insurance Co. (1996), 1996 CanLII 8109 (ON SC), 27 O.R. (3d) 479 (Gen. Div.), rev’d on other grounds (1999), 1999 CanLII 3051 (ON CA), 42 O.R. (3d) 641 (C.A.), aff’d 2002 SCC 18 (CanLII),  1 S.C.R. 595.
There must be a causal connection between the non-compensable prejudice and the amendment. In other words, the prejudice must flow from the amendments and not from some other source: Iroquois, at paras. 20-21, and Mazzuca v. Silvercreek Pharmacy Ltd. (2001), 2001 CanLII 8620 (ON CA), 56 O.R. (3d) 768 (C.A.), at para. 65.
The non-compensable prejudice may be actual prejudice, i.e. evidence that the responding party has lost an opportunity in the litigation that cannot be compensated as a consequence of the amendment. Where such prejudice is alleged, specific details must be provided: King’s Gate Developments Inc. v. Drake (1994), 1994 CanLII 416 (ON CA), 17 O.R. (3d) 841 (C.A.), at paras. 5-7, and Transamerica Life Insurance Co. of Canada v. Canada Life Assurance Co. (1995), 1995 CanLII 7105 (ON SC), 25 O.R. (3d) 106 (Gen. Div.), at para. 9.
Non-compensable prejudice does not include prejudice resulting from the potential success of the plea or the fact that the amended plea may increase the length or complexity of the trial: Hanlan v. Sernesky (1996), 1996 CanLII 1762 (ON CA), 95 O.A.C. 297 (C.A.), at para. 2, and Andersen Consulting, at paras. 36-37.
At some point the delay in seeking an amendment will be so lengthy and the justification so inadequate, that prejudice to the responding party will be presumed: Family Delicatessen Ltd. v. London (City), 2006 CanLII 5135 (ON CA), 2006 CanLII 5135 (Ont. C.A.), at para. 6.
The onus to prove actual prejudice lies with the responding party: Haikola v. Arasenau (1996), 1996 CanLII 36 (ON CA), 27 O.R. (3d) 576 (C.A.), at paras. 3-4, and Plante v. Industrial Alliance Life Insurance Co. (2003), 2003 CanLII 64295 (ON SC), 66 O.R. (3d) 74 (Master), at para. 21.

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