Can self-employed people pay social security?

Yes, you can. Social security payment method: if an individual participates in the insurance in his own name, he can't pay back the missed payment, and only the missed payment caused by the unit can pay back the five insurances; If the unit does not declare (does not open an account), it can only pay the pension; After paying for a period of time, you can find an agent to pay.

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