Actual spending data (paid invoices) are available only for a tiny fraction of the government. First office to make such data accessible was the Ministry of Finance, which publishes invoices backdating to 2010. They have also built their own visualisation app to present the data.
Data: https://data.mfcr.cz/cs/dataset/prehled-faktur-ministerstva-financi-cr
Visualisation: https://data.mfcr.cz/supervizor/
Couple of ministries (Justice, Regional development) inspired by them built their data own catalogues, even though the coverage is modest.
In 2016, after a long political fight, a register of contracts awarded was launched. While the data is incomplete (e.g. some prices not published due to trade secret), it is a good info source. Data are also available as monthly XML dumps. However, this will not satisfy the "actual detailed spending on national level" criteria. I just wanted to mention the initiative, because it was quite a big step towards govt transparency. https://smlouvy.gov.cz/
