It seems the CFA currency of Central Africa or XAF which is the single currency of six central Africa countries (Cameroon, CAR, Chad, Republic of Congo, Equatorial Guinea and Gabon) will be devaluated (last January, IMF Managing Director and French Economy and Finance Minister already suggested this assumption). In fact, that currency is linked to Euro based on a fixed exchange rate handled by the french National Bank. This situation is sustainable as long as those countries are capable to grant a fixed portion of their foreign currencies reserves in a kind of adjustment account. That said, the sustainability of such system depends on a high level of exports from that countries. However, those ones are mono-product based and any lower commodities market price impact negatively their trade balance. That what happened since the market price of their main source of exports (I mean Crude oil and LPG) collapsed back to 2014... If the devaluation of that currency occurs in coming months or quarters, companies located in Eurozone which have interests in the region will notice a huge impact on their Income Statement. Let's take an example: subsidiaries which operate locally pay their local charges such as payroll and Tax in the local currency and report the associated accounting records in Euro for consolidation purposes. As long as the pair EUR/XAF is stable, there is no P/L impact of those transactions. But, when the currency will be devaluated, those subsidiaries will be obliged to record transactions of the associated period in the update rate per IFRS accounting policy. So, for the first time since 01/01/2002, they will report currency exchange gain/loss by implementing a kind of process called FX or FOREX report. Since the reference currency is EURO, It will be an exchange gain in local books since the rate supposed to increase from 1 EUR for 655.957 XAF currently to 1EUR for 1300 XAF when the devaluation will happen. The impact will be permanent and done once time (I mean by the time the devaluation will occur) unless the concerned states decide to give up that currency.
NB: Only XAF is supposed to be devaluated not XOF used by 08 west african countries (Ivory Coast, Senegal, Mali, Burkina Faso, Benin, Togo, Niger and Bissau Guinea). The mechanism is the same but here, the currency is supposed to be appreciated permanently (I mean 1 EURO for 500 XOF instead of 1 EURO for 655.957 XOF currently). So, the opposite impact will happened, EUROZONE entities subsidiaries will reconigze an exchange loss...
Source: http://www.lasemaineafricaine.net/images/pdf/3701.pdf (in french, refer to page 6)