By the 1340s and 1350s, Parliament had asserted and largely established an exclusive right to grant new taxes (Waugh 1991, p. 203; Sacks 1994, p. 19; Payling 2009, p. 76). Thereafter, until the Revolution, taxation was supposed to proceed as follows. The monarch would ask for new taxes and, in exchange, offer some general remarks about the purposes to which the new revenues would be put. Those purposes were typically war-related and invoked the doctrine of necessity (Sacks 1994, pp. 17–18). In my lingo, the monarch offered to “sell” Parliament some platforms – sovereign promises about expenditure – in exchange for taxes. If MPs liked what they heard, they could “buy” the platform by granting taxes.

Virtually all platforms before the Revolution were royal; very few were embedded in statutes. Thus, the monarch could change his or her mind about the proper use of the revenues at will. Even if the monarch did not abandon his/her original promise, however, Parliament typically had little idea whether it was being honored, as MPs lacked even the most basic accounts of the public revenues and expenditures.

The low credibility of royal platforms led, especially during the Stuart years, to the Commons denying supply. Why buy a platform whose performance one cannot verify and can be changed at royal whim? The Crown, anticipating that its dodgy pledges would elicit no new taxes, did not summon Parliament – and sought to find revenues without it.

There were only two logical ways out of the fiscal impasse facing Stuart England. One, the Stuarts’ preferred solution, was royal absolutism (Pincus 2009). The other required making sovereign promises about expenditure more credible, so that bargains between the tax-granting Commons and the platform-peddling Crown would no longer fail so often.

After the Revolution, Parliament simultaneously defended against absolutism and reengineered the credibility of platforms. To make platforms harder to change legally, Parliament embedded them in statutes, in what were called appropriations. To bolster its ability to verify that promises were kept, Parliament required executive officials to provide vastly more information about the public finances. To enhance its ability to punish ministers for violating its instructions, Parliament forced ministerial responsibility on a reluctant monarch.

Inextricably connected to the rapidly evolving appropriations-audit- punishment system was the emergence of ministers as the monopoly brokers of the taxes-for-platforms market.