Royal assent
The power of parliament to pass bills was often thwarted by monarchs. Charles I dissolved parliament in 1629, after it passed motions critical of and bills seeking to restrict his arbitrary exercise of power. During the eleven years of personal rule that followed, Charles performed legally dubious actions, such as raising taxes without parliament's approval. After the English Civil War, it was accepted that parliament should be summoned to meet regularly, but it was still commonplace for monarchs to refuse royal assent to bills. In 1678, Charles II withheld his assent from a bill "for preserving the Peace of the Kingdom by raising the Militia, and continuing them in Duty for Two and Forty Days," suggesting that he, not parliament, should control the militia. The last Stuart monarch, Anne, similarly withheld on 11 March 1708, on the advice of her ministers, her assent from a bill for the settling of Militia in Scotland. No monarch has since withheld royal assent on a bill passed by the British parliament.

Q: What is one action this monarch took that is typically left to the discretion of parliament?
raising taxes