When implementing a new HRIS software system, it is very important to have the new system functioning properly before abandoning the prior system. This process, called parallel testing, involves operating both systems simultaneously for several months, perhaps for an entire year, before discontinuing the former system. Inconsistencies between the two systems need to be resolved to make certain that the new system is operating as expected, especially when unique situations arise, such as overtime calculations that include production bonuses, benefits changes, reimbursements for unused vacations, and intermittent FMLA leave calculations.