For many years, the legal protection of personal data prohibited the analysis of individual census data in the Czech Republic; thus, this is the first article to provide a detailed analysis of data on religion. Employing individual data for the whole population, the authors confirm several trends in the recent religious development of the country, including general out-churching, the expansion of certain smaller denominations, and, especially, an increase in the number of people declaring themselves religious, but unwilling to claim allegiance to any particular church. Of even greater importance is the observation that almost half the population refused to declare their religiosity (or the absence thereof) in the last (2011) census. The article focuses especially on this group, providing an attempt to characterise them socio-demographically. The "non-fillers" stand somewhere between believers and unbelievers who completed the census and share certain characteristics with both groups. It can be assumed that a (slight) majority of this group consists of unbelievers as well as an (also rather small) minority of church members, both of which groups chose not to express their non/religiosity via the census. However, such "non-fillers" differ significantly from the religious population – both with and without denomination. At the same time, refusing to declare a personal religious affiliation is often connected with the refusal to complete other census items, which might be seen as a sign of the distrust of, or resistance to, the state as the most important collective body. From this point of view, the increase in secularisation and other changes in Czech religiosity could be considered to represent expressions of a wider divergence from all types of social bodies including state authorities.