That's the problem and always has been.
Now, if anyone is curious as to what powers are held by Holyrood and what are still held be Westminster, BBC Scotland put this handy guide up:
Election 2017: Who has power over what in Scotland?
The catch is with the current hybrid arrangement is that funding in Scotland isn't fully devolved. It's still linked to what's spent in England via the Barnett Formula. Until that link is severed it's still possible for a Scottish MP to vote on funding arrangements in England. However, the risk is that full fiscal control would then effectively make Scottish Independence cost neutral and it also has the potential to create an economic threat to England.
Mike.