The work is devoted to topical issues of legal regulation of the application of the exchange rate for the purpose of customs assessment. The author analyzed the regulatory framework of the EAEU and the Russian Federation governing such issues. The problem of reliable determination of the amounts of additional charges, which are paid in a currency different from the currency of the contract, in terms of the application of the exchange rate, has been identified. The author analyzed the judicial practice on this issue. Based on the analysis, the author formulated conclusions on the procedure for applying the exchange rate in case of payment of additional charges to the customs value in a currency different from the contract currency.