Is it invalid for Beijing medical insurance to stop paying social security for three months?

The previous payment period is not invalid.

If the payment is suspended for no more than 3 months, it can be paid back and accumulated, but the medical insurance benefits cannot be enjoyed during the suspension period; If the payment is interrupted for more than 3 months, it will not be paid back, and it can only be paid again, and it is also calculated cumulatively.

Medical insurance payment is related to the enjoyment of treatment. Enterprise employees can enjoy medical insurance benefits normally from the month following the insured payment, and relevant medical insurance benefits will also stop after the insurance is stopped, but the system data and payment period will not be cleared.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.