In the past, the requirements were not strict, and paying social security money for a few years could increase the length of service. Not now, you can only calculate the length of service from the year when you start paying social security. If you don't pay social security in the middle, it seems that you don't have to pay it, but you can count the length of service if you make up. It doesn't matter if you spend some time now, lest you lose money when you retire in the future. In short, as long as you pay the social security money, you will definitely count the length of service.