Legally, you must accommodate the employee to the point of undue hardship. Modification of work hours is probably the most common accommodation made for employees returning to work from a medical absence. If 4 days per week is undue hardship--and that's a big IF--you need to consider alternatives. The best way to explain this is to go directly to the horse's mouth--the horse in this case being the Ontario Human Rights Commission. Here's what they say on this topic. Go to http://www.ohrc.on.ca/en/policy-ableism-and-discrimination-based-disability/8-duty-accommodate#_edn159 if u want to read this directly or see the entire Accommodations guidance publication. Hope this answers your Q. ****** 8.3.2.1 Alternative work There is a duty to accommodate a person in their pre-disability job wherever possible. However, it is recognized that this may not always be feasible. Human rights case law recognizes that employers have a duty to consider temporary and permanent alternative work for people who can no longer remain in their position even with accommodation.[158] This duty includes diligently investigating positions and proposing job options[159] that are within the person’s functional limitations.[160] Accommodation may include job restructuring, job bundling,[161] reassignment to open positions, or retraining for alternative positions if that would not constitute undue hardship for the employer. Employers should canvass available posts that allow the employee to maximize his or her skills and abilities.[162] Temporary alternative work The term "alternative work" means different work or work that does not necessarily involve similar skills, responsibilities and compensation.[163] Temporary alternative work may be an appropriate accommodation either in a return to work context, or in a situation where a disability renders an employee temporarily unable to accomplish the pre-disability job. Temporary alternative work can be an appropriate accommodation to assist a person where the nature of the disability and its limitations are temporary or episodic. Permanent alternative work When an employee asks to be reinstated in a previous position, the employer must make the appropriate inquiries to assess whether the employee is fully able to carry out the essential functions of the job. The returning employee must be given an opportunity to prove his or her ability to perform the pre-disability job.[164] Where the employee can no longer perform the pre-disability job, with or without accommodation, the employer should consider permanent alternative work.[165] The duty to accommodate may include some workplace reorganization.[166] For example, it may require employers to consider placing an employee with a disability into a vacant position without requiring that person to compete for the position.[167] The vacant position must be vacant within a reasonable amount of time, but the employer is not required to “promote” the employee. To the greatest extent possible, the vacant position must be equivalent to the current one. When reassignment takes place, the person must be qualified for the reassigned position.

Example: An employee with a disability returns from a disability leave and is considered for alternative work. There are two other positions available at the company. He is generally qualified for one of these positions, but does not know how to use a computer program that is required to do the essential duties of this job. The employer sends the person on a training course to learn the computer program. The employee is then qualified for the position.

The duty to accommodate does not require the employer to completely alter the essence of the contract of employment, that is, the employee’s duty to perform work in exchange for remuneration.[168] The duty to accommodate does not require an employer to provide “make work” or “to create a job that is not productive or that, in the employer’s view, does not need to be done.”[169] Nor is an employer required to employ two employees to do the job of one.[170] In the final analysis, the employee must be able to perform a useful and productive job for the employer.[171] 8.3.2.2 Return to work Accommodating a person who has been absent from work may involve any of the above forms of accommodation but also raises unique issues. People who return to work after an absence related to a Code ground are protected by the Code.[172] They generally have the right to return to their original job (the pre-disability job). Both employers and unions must co-operate in accommodating employees who are returning to work. Accommodation is a fundamental and integral part of the right to equal treatment in the return to work context.[173]

Example: In one case, a woman who had been off for several months for a series of surgeries informed her employer that she planned to return to work. The HRTO found that her employer discriminated against her when it required her to provide a “clean bill of health,” tried to require her to sign a letter agreeing to a finite cap on future medical leave, and asked her to complete a retraining period before it would consider whether she could return to work. The HRTO affirmed that the woman was entitled to her previous job. The employer acted in a discriminatory way when it merely offered to consider rehiring her.[174]

The right of people with disabilities to return to work exists if the worker can fulfil the essential duties of the job after accommodation short of undue hardship.[175] If a person cannot fulfil the essential duties of the pre-disability job, despite the employer's effort to accommodate short of undue hardship, the employer still has an obligation to canvass alternative work possibilities, as outlined above. Ultimately, as stated above, the person with a disability must be able to perform a useful and productive job for the employer. Under the Code, there is no fixed rule as to how long an employee with a disability may be absent before the duty to accommodate has been met. This will depend on the ability of the employee to perform the essential duties of the job considering the unique circumstances of every absence and the nature of the employee’s condition, as well as circumstances in the workplace.[176] Also important is the predictability of the absence, in terms of when it will end, if it may recur and the frequency of the absence. The employee’s prognosis and length of absence are also important considerations. It is more likely that the duty to accommodate will continue with a better prognosis, regardless of the length of absence. The duty to accommodate does not necessarily guarantee a limitless right to return to work.[177] On the other hand, a return to work program that relies on arbitrarily selected cut-offs or that requires an inflexible date of return may be challenged as a violation of the Code.

Example: In a case that dealt with a modified work program that featured a “90-day” rule that deemed temporary restrictions of more than 90 days to be permanent, the HRTO stated: “A general employment-related human rights principle is that when an employee is temporarily unable to perform a job because of disability, the employer is obliged to keep the employee’s job available so that the employee can return to it when the disability improves to the point the employee can return to the job. This is a form of accommodation of the person’s disability related needs. The obligation to keep the employee’s job available does not extend indefinitely, and is limited by undue hardship involved in keeping the job available, but it generally extends for more than three months.”[178]

Ultimately, the test of undue hardship is the relevant standard for assessing return to work programs. .