AbstractDigital accessible knowledge of biodiversity data is an increasingly important source of information in studies of biogeography and conservation. These databases can also reveal temporal, spatial and taxonomical gaps in biodiversity documentation, even in areas that have been intensively studied and from where accurate species lists are available. Therefore, revealing these gaps may help allocating collecting efforts, conservation priorities and strategies for improving database curation. Here, we evaluate potential shortfalls for flowering plants in a tropical hotspot, the Brazilian Atlantic Forest, by cross‐referencing two online repositories of biodiversity data (the Global Biodiversity Information Facility – GBIF – and the Brazilian Flora 2020 floristic database – BFG). We aimed to evaluate the congruence between those repositories, highlighting tendencies in current documentation for this area. We found that from the 7220 reported flowering plant species endemics to the Atlantic Forest, 1573 (22%) have no valid spatial data in GBIF, and 75% of all of the 605,951 records do not present valid spatial information. Most of the missing information is related to species known only from few and old collections with absent or inaccurately georeferenced data. This lack of information may cause a large impact in spatial studies, especially for rare and threatened species. Nevertheless, our analysis also shows that spatial information for the filtered data is highly congruent between GBIF and BFG data, indicating relatively high availability of quality data in large repositories after standard and automatized cleaning procedures. Still, good practices to decrease the impact of losing data are recommended, including more investment in field collections, targeting poorly known species and returning cleaned spatial datasets to online repositories after taxonomic revisions.