In my opinion, they won't be able to track your income unless declared. Cause if Bitcoin is a system that can be tracked by centralized authorities like banks and government, where's the sense of it being decentralized.
They can track using the bank details, because banks may be asked to provide details if account is being open for btc transactions or any suspicious transactions happening regularly than those details will be forwarded to them and then you will be under scanner.
There is no tax until we keep using bitcoin as bitcoin but still it is not possible yet so we need to convert our bitcoin into fiat so bank is essential so our earning will be recorded so we must need to pay taxes according to our income.