Under the Enlistment Act, all male Singapore Citizens and SPR will be scheduled for enlistment upon reaching the age of 18 years. Singapore Permanent Resident (SPR)'s granted under the Professionals/Technical Personnel and Skilled Workers (PTS) Scheme are administratively exempted from NS. NS is a key institution that is vital to the security and defence of Singapore. Like citizens, SPRs also enjoy the security and stability made possible by the contributions of National Servicemen. As such, it is the duty of every Singapore male citizen and SPR to serve NS under the Enlistment Act. This obligation to serve NS is made known to SPRs at the point of application for Permanent Residence.