Cookish v. Paul Lee Associates Professional Corporation 2013 ONCA 278 holds:
 Ms. Pagliaroli submits on behalf of the appellant that an assessment officer does not have the authority in any circumstances to deal with disputes concerning the retainer, other than disputes regarding quantum alone. In my view, while that is true where an order is obtained on requisition under s. 3(1), it is not accurate to say that such authority may never be given to an assessment officer. However, the preferable procedure is for a judge to determine these issues. Once they have been resolved, the bill may then be referred to the assessment officer for a determination of the proper quantum, if necessary.
 I arrive at this conclusion for the following reasons.
 An assessment officer has no inherent jurisdiction and must therefore find his or her authority in some statutory source or in the Rules of Civil Procedure. This principle has been applied to masters and, by extension, registrars charged with issuing orders for assessment: see Davies, Ward & Beck v. Union Industries Inc. (2000), 48 O.R. (3d) 794 (C.A.), at para. 13; Crooks v. Clement,  O.J. No. 5436 (Gen. Div.), at para. 11. By further extension, this principle also applies to assessment officers.
 The position of assessment officer is created by s. 90 of the Courts of Justice Act, R.S.O. 1990. c. C.43, but it is questionable whether that section itself provides an assessment officer with authority to assess a solicitor's bill vis-à-vis a client. While s. 90(3) provides jurisdiction "to assess costs in a proceeding in any court", that provision more likely provides authority for the assessment of costs as between litigants in a proceeding rather than for the assessment of a solicitor's bill as between the solicitor and the client. In the latter situation, an assessment officer's authority is rooted either in the Solicitors Act or in reference provisions found in Rule 54 of the Rules of Civil Procedure, in my view.
 Subsection 3(1) of the Act and the jurisprudence relating to it make it clear that an assessment officer has no jurisdiction to determine disputes relating to the existence, nature, terms or extent of a retainer agreement where the order is obtained on requisition. There are only two exceptions to this proposition: (i) where there is really no legitimate dispute regarding the retainer; or (ii) where the dispute relates only to the quantum of the bill: see Paoletti v. Gibson, 2009 ONCA 71, 308 D.L.R. (4th) 179, at paras. 28-30; and Park v. Perrier (2005), 200 O.A.C. 377 (Div. Ct.), at para. 66.
 While an assessment officer is expressly excluded from exercising the authority to resolve disputes regarding the retainer where the assessment order is obtained on requisition under s. 3(1), there is nothing in the Act that expresslygrants an assessment officer the authority to do so in any other circumstances. The route to that authority – to the extent it should be exercised – lies in the reference procedure provided in the Rules, in my view.