For 2023 tax returns the official FTA exchange rates are:

    IncomeWealth
USD1   =  CHF 0.89880159CHF 0.841624
EUR1   =  CHF 0.97165064CHF 0.929700
GBP1   =  CHF 1.11706498CHF 1.072875

Official foreign exchange rates as of 31 December 2023 are available here. In this list are also included rates to apply for the main cryptocurrencies (these are found with the list of national currencies). These need to be reported in the tax declaration.

BTC 1 = CHF 35,541.630896
ETH 1 = CHF 1,948.008419
BCH 1 = CHF 219.587313