The social office changed the due dates for the advances paid during the year. 

The due date for payment of social insurance (and illness insurance) advance was 20th day of following month. (eg. for October you paid till 20.11.).

From January 2019, the due date is the last day of the current month. It means that insurance for January 2019 must be paid till 31.1.2019.

The insurance for December 2018 should be paid already till 31.12.2018; however if you dont pay it, than there is no penalty and you will pay it after filing the Statement of income (Přehled OSVČ).

If you pay anything in January, than it will be considered as advance payment for January 2019!

Please note, that the due dates are dates when your insurance must be already at the bank account of the social insurance office, not the date when you pay it.

New minimul payment for Illness insurance is 138 Czk (valid from January 2019)

New minimum payments for social insurance (duchodove pojisteni OSVC) is 2388 Czk (valid from the month following the filling of Statement of income for 2018).