You can set or change your base currency in the Settings > Portfolio:
ℹ️ Find and select your base currency
By default, top 25 most popular fiat currencies are shown in the dropdown box, but you can start typing to search for the fiat currency you want to use.
Base currency can be set to any fiat currency we support and is used throughout your Koinly account:
On the dashboard, your portfolio value and gains are provided in base currency
Each transaction on the transactions page is valued in base currency
Cost basis of your assets is recorded and tracked in your base currency
Reports that you download use the base currency
Selecting your base currency does not mean that you cannot purchase crypto using a different fiat. You can transact with whichever currency you like but the market prices, cost basis and capital gains/losses will all be calculated in your base currency.
Choosing the base currency
It is recommended to set it to the currency you will be reporting your taxes in or the currency you use to buy most of your cryptocurrencies.
Using a different base currency than the one you later file taxes in may result in unpleasant surprises during tax season when you change your base currency to the one required by your country and see completely different results than before (see "Why did my gains change" section below)
Changing the base currency
If you change the base currency of your portfolio, Koinly will recalculate all your transactions in the new fiat currency.
Changing the base currency is non-destructive. You can change it back later to the same currency you had, and all the calculations will go back to the way they were.
Why did my gains change?
☝️ Changing the base currency often completely changes your gains
If you change your base currency, it usually results in completely different capital gains calculations. The change is caused by price fluctuations between the previous base currency and the new one.
These price fluctuations affect the tracked cost basis of your assets (cost of acquisition) and the worth of those assets upon disposals (market value), changing the final gain/loss calculated.
Example: How changing the base currency affects your gains
Example: How changing the base currency affects your gains
The simplest example that explains it is using stablecoins
Base currency USD:
If your base currency is USD, selling one dollar-pegged stablecoin to another usually doesn't result in any gains or losses (unless some fees were involved) as the token is always worth $1 and the cost basis will also be $1 per 1 USDC.
Base currency EUR:
If you change your base currency, the situation is suddenly different. You now have a loss on the later sale of USDC for USDT, because the cost basis of 1000 USDC (how much you paid for it, now valued in EUR) is higher than the value of 1000 USDT you now acquired (now valued in EUR).
This is due to the changes in EUR/USD rate between the two transactions.