Definition - What does Backfilling mean?
Backfilling is a type of employee reshuffling where one employee moves on to a new position within the company, and a different employee takes the place of the the one who moved. Backfilling is relevant in employment and tax law because it is can affect how many employees are on the payroll, whether or not benefits and salaries change, etc.
Justipedia explains Backfilling
When an employer needs to fill a position, he or she can either hire from the outside or from the inside. If he or she hires from the outside, that can mean adding an additional person to the payroll. However, if the employer backfills the position, then the same number of people could still be on the payroll. So, whether or not an employer backfills a position can impact important tax and/or other legal information within the corporate structure.