In this article it is claimed that (1st paragraph):
Especially in England and Ireland, it became the drink of choice, and through taxation, came to contribute 30%-50% of the nation’s revenue.
This must be a historical figure because it doesn't seem to hold true for today:
The Scotch Whisky Association mentions that, as of 01 May 2015,
Exports generated £3.95 billion for the UK balance of trade
I take that to be whisky's contribution for the month of April 2015, though the website doesn't specify. According to this figure from the UK Trade Office, the total value of goods exports for 2015 was between 20-25 billion pounds. This doesn't take into account domestic consumption. Therefore, Whisky doesn't contribute anywhere near 30% of the UK's income. What I'm not clear on is whether the Trade Office accounts presents the good's tax value only, or the net value.
Was there a time in history when Whisky taxation contributed anywhere near 30-50% to the UK's coffers?