According to PwC’s Czech tax summary:

"Social security taxes are obligatory for an individual who performs a gainful activity in the Czech Republic, unless an EU regulation or social security treaty states otherwise."

Source: PwC – Czech Republic / Individual / Other taxes
Read full summary here

🇨🇿 When You Do Pay Czech Social Security

• If you're employed by a Czech company → your employer pays it for you.
• If you're a freelancer (OSVČ) in Czechia → you must register and pay it yourself.
• If you're a foreigner working from Czechia for clients or companies abroad → you typically pay, unless you provide proof of exemption (e.g. A1 certificate).

🌍 When You May Be Exempt

You may not have to pay into the Czech social security system if:

• You’re covered under EU Regulation 883/2004 and have an A1 certificate from another EU country.
• You’re from a non-EU country that has a social security treaty with the Czech Republic (e.g., USA, Canada, Australia), and you meet the treaty’s exemption conditions.

📌 Example:

An American developer working remotely from Prague for a U.S. company might stay covered under U.S. Social Security for 5 years if they file the correct certificate through the U.S.–Czech social security agreement.

✅ Bottom Line: Unless exempt by treaty or EU regulation, foreigners performing gainful activity in Czechia generally must pay Czech social security.