If you are an entrepreneur, it is your obligation to pay your insurance on your own. If you apply for a long-term visa, a long-term residence permit or an extension of a residence permit once you are already in the territory of the CR, you are obliged to arrange commercial health insurance in the scope of comprehensive healthcare.
You also have to pay social insurance on your own. It is usually paid from the beginning of the business activity in a form of monthly premiums. The premiums are paid to the Regional Social Security Administration (RSSA; the Czech abbreviation is OSSZ). The deadine for each month is the last day of the month.