Based on paragraph 48 of Sweezey v Sweezey, 2016 ABQB 131. Although Cunningham v Seveny, 2017 ABCA 4 thereafter changed the law, at least one decision, Zdyb v Zdyb, 2017 ABQB 44, has adopted the Sweezey framework, less the requirement to exchange all supporting documentation.
It's preferable that the client's bookkeeper, in conjunction with the client, prepare the Business Expense Disclosure Statement. However, be aware that some bookkeepers and accountants will refuse to complete any tasks relating to the court, in which case you and your client may need to complete this after looking at expenses or general ledger statements.
This precedent was first handed out at a CBA Family Section meeting (with Micia Kawulka presenting on the topic of business expenses) on February 9, 2017.