TLDR: Conversion rules vary depending on the tax context. For platform operators (DAC 7), use the ECB's annual average exchange rate. For the DST, apply the EU Official Journal rate on the first day of the month of receipt. For the disposal of digital assets, convert at the rate on the day of each transaction.
General rules for platform operators (DAC 7)
Platform operators must convert consideration received in foreign currencies using the annual average exchange rate published by the ECB for the year in question. This rule applies specifically to the reporting obligations under DAC 7.
Conversion for the DST (Digital Services Tax)
For the DST, amounts received in foreign currencies must be converted into euros using the exchange rate published in the Official Journal of the European Union on the first day of the month of receipt. This rule is specific to the DST and does not apply to other tax contexts.
Conversion for the disposal of digital assets
In the case of the disposal of digital assets, if the price is expressed in a currency other than the euro, the conversion must be carried out at the exchange rate in force on the date of each transaction. This rule applies to determining the taxable base of the capital gain.
Special cases and simplifications
For platform operators, it is permitted, as a simplification, to convert all currencies into a single intermediate currency (e.g., the euro) before proceeding with the final conversion, provided that this method is consistent and documented.
Exclusions and limits
The conversion rules described above do not apply to transactions outside the explicitly mentioned contexts (DAC 7, DST, disposal of digital assets). No other conversion method is authorised for these specific cases.
Clarifications on official sources
The exchange rates used must come from official sources: ECB for annual conversions, EU Official Journal for the DST, and the daily rate for the disposal of digital assets. No approximation or rounding is tolerated for conversions between the euro and the currencies of EU Member States.