I worked for a company that decided to have a “summer workday” program (work 4 days in the summer), so employees got every Friday off all summer and then they were to work extra time each week in the September to December period to offset the hours they did not work in the summer. Sounded good on paper but it was a nightmare for HR and Payroll staff. This was in a company with over 1200 employees! If an employee left the company or went on Maternity or sick leave with EI, I had to recalculate every summer pay cheque, adjusting CPP, EI and taxes and then adjust their final pay, record of employment etc. I have not had specific experience with “salary deferrals” but the key is to ensure the rules of the program are clear up-front so everyone knows the consequences of choosing to defer salary.