IOF (Imposto sobre Operações Financeiras) is a Brazilian tax that applies to certain financial transactions. Here is how it works with AstroPay.
When IOF is charged
Converting BRL to a foreign currency: IOF rate is 0%. AstroPay covers this tax.
Using BRL for international purchases: IOF rate is 0%. AstroPay covers this tax.
Converting a foreign currency to BRL: IOF rate is 0.38%. This is the only scenario where IOF is charged to your transaction.
Summary
In most cases, you pay no IOF when using AstroPay with BRL. The 0.38% rate only applies when you convert foreign currency back into BRL.