It seems not to have official estimates about the proportion of the population incurring out-of-pocket payments for health services. However, a study conducted by the Credit Protection Service Brazil (SPC Brasil) and by the National Confederation of Stores Owners (CNDL) with 1,500 people from large capitals showed that, from the 70% of people who did not have private health insurance, 25% made out of pocket payments for private services (CNDL, 2018).

References:

CNDL. (2018). Gastos dos Brasileiros com Saúde.