Partial double entry of data collected through the paper versions of the questionnaires by two key-entry operators was required as an effective means of detecting and reducing systematic or incidental data cntiy errors. Here, the advantage of the online data collection option becomes evident because data entry is already predefined in terms of value ranges and variable types. The data submitted by national centres was monitored closely by the TALIS 2018 International Research Consortium to verify the completeness and quality of the data received.