From the CNB Press Release: 

The CNB Bank Board approved the new rate for exposures located in the Czech Republic at its meeting on 6 December 2017. “A number of factors spoke in favour of the increase. Rapid growth in bank loans, especially loans to households for house purchase and consumption, is continuing,” explained Vice-Governor Vladimír Tomšík. “This buffer is aimed not at stopping lending, but at creating a buffer for worse times in the current good times,” he added.

The countercyclical capital buffer was introduced as an important macroprudential policy instrument in the European Union in 2014. Obliged institutions are required to create this buffer on the basis of the regulator’s instructions in periods of excessive growth in lending. Excessive lending growth usually increases financial imbalances and leads to a rise in systemic risk. By contrast, at times of falling economic activity, accompanied by rising credit losses, this buffer should be released so that non-financial corporations and households continue to have access to loans without excessively tight conditions.

The CNB increased the rate from zero for the first time in December 2015, with effect from 1 January 2017. The Bank Board decided to raise it further to 1.0% in June 2017, with effect from 1 July 2018.

Read more about Countercyclical Buffer Rates here (source: CNB) and here (source: European Systemic Risk Board)