The September 2023 update to the Poverty and Inequality Platform (PIP) involves several changes to the data underlying the global poverty estimates. In particular, some welfare aggregates have been revised, and the CPI, national accounts, and population input data have been updated. This document explains these changes in detail and the reasoning behind them. Moreover, 63 new country-years have been added, bringing the total number of surveys to more than 2,200. Global poverty estimates are reported up to 2019 and earlier years have been revised. Regional poverty estimates in 2020 and 2021 are reported only for regions with sufficient survey data coverage during the COVID-19 pandemic.