Seven of the eight EU countries not yet using the euro as their legal tender undertook to adopt the common currency in the future. However, the actual moment of adoption may influence, e.g. the attitude of the population (households). Other needs for the use of the euro have a business sector that is managed considering current market conditions and opportunities. The prerequisite of this article is that within the non-EMU EU economies, due to the close ties to EMU members and the prospect of a future, albeit often uncertain, approach to the euro area, the gradual euroization of businesses takes place. Among other things, euroization should be reflected in foreign trade, namely in the currency of invoicing. Using the Eurostat data from 2010–2018 on import and export and the currency of non-EMU countries invoicing to third countries expressed in EUR, USD, national and other currencies, the links between invoicing currency, size of economies and exchange rate regime were sought. The aim was also to describe the actual trend of invoicing international trade to third countries outside the EU. According to the results of the analysis, it was found that the block of non-EMU countries rather euroizes and the importance of the national currency is rather declining. The level of growth of the share of the euro and the decline of the national currency has a different intensity for imports and different for exports. At the same time, it was found that in the case of imports in EUR and NC and exports in EUR, a possible relationship between the invoicing currency and the exchange rate regime can be identified. Last but not least, it was found that in the case of invoicing in EUR and NC (national currency), there is a relationship between the size of GDP and the invoicing currency.