The phrase "mere formality" means that something is done as a required procedure or tradition, but it doesn't hold much importance or have much effect on the overall outcome. Full definition
When motivated by your innate interests and an authentic spirit of service, opportunities tend to arise wherein the cost becomes mere formality. (thecollegeinvestor.com)
Management therefore must ensure that rules that prescribe behavior are not mere formalities because people in positions of authority disregard and show little respect for them. (slaw.ca)
Reference checks are no longer mere formalities on the application page. (biginterview.com)