The BS Filled Total Column Ozone (TCO) database version 3.5.1 provides a gap-free extension of the NIWA-BS Total Column Ozone database version 3.5.1 (doi:10.5281/zenodo.4535293) which combines TCO data from multiple satellite-based instruments to create a single near-global daily time series of ozone fields at 1.25° longitude by 1° latitude spanning the period 31 October 1978 to 31 December 2019. The construction of NIWA-BS TCO was initially maintained by the National Institute of Water and Atmospheric Research (NIWA) and now by Bodeker Scientific (BS). The latter also developed the BS Filled TCO database published here. While the BS Filled TCO database has the same resolution and covers the same period as NIWA-BS TCO, any missing data have been filled using a machine learning-based method that regresses the NIWA-BS TCO database against NCEP CFSR reanalysis tropopause height fields and potential vorticity (PV) fields on the 550 K surface. Uncertainties in the filled TCO fields are provided on every datum and these uncertainties reflect the data availability, i.e. the uncertainty is smaller where measurements are available compared to regions where filling of the data was required. Please note: For the reasons detailed in this document, versions 3.5.x of the BS Filled TCO database and of the NIWA-BS TCO database should not be used henceforth for trend analysis and, as such, we have updated the version 3.4 of NIWA-BS Combined TCO database to the end of 2019 (now referred to as version 3.4.1 of the database) as a replacement. You will find a link to version 3.4.1 under the link provided above. The data are available in daily, monthly or annual resolution. Please note the following for the data in annual resolution: There have to be at least 12 valid monthly values within a year to calculate a valid annual mean. Therefore, no annual mean is available for the year 1978 as the record only starts on 31 October 1978. Please email greg@bodekerscientific.com and let us know which data set you downloaded and what your intended purpose for the use of the data is. You will then receive updates if an improved version becomes available.