To derive reliable demographic indicators, appropriate data on population exposures are needed. Access to such data is becoming increasingly challenging in many countries due to factors such as the growing diversity of international migration patterns and the trend towards replacing full censuses with register-based censuses. Germany represents a particularly challenging case in this respect. Before Germany implemented its first register-based census in 2011, the country had not conducted a census for more than two decades. This census revealed that the number of people living in Germany in 2011 was about 1.5 million lower than the previous official post-censal population estimates for that year indicated. It is likely that a large portion of this discrepancy had existed for quite some time prior to 2011. Due to the long inter-censal period, the Federal Statistical Office of Germany decided not to produce backward-adjusted population estimates by single-year ages and sex for the whole period. The main aim of this paper is thus to make such detailed adjusted inter-censal population estimates available. While we have to take the peculiarities of the German case into account, our evaluation of different strategies offers important insights for developing a generalised methodology to adjust inter-censal population estimates for globalised countries that face challenges in ensuring the proper registration of migration events. We discuss four alternative approaches for deriving adjusted inter-censal population estimates. The results suggest that even for a rather complicated case like Germany, a relatively simple approach seems to work reasonably well. Finally, we demonstrate to what extent the implemented adjustments affect mortality indicators. The adjusted inter-censal population estimates for Germany and its federal states are provided in the online data appendix.