The English Protestant Reformation was imposed by the English Crown, and submission to its essential points was exacted by the State with post-Reformation oaths. With some solemnity, by oath, test, or formal declaration, English churchmen and others were required to assent to the religious changes, starting in the sixteenth century and continuing for more than 250 years.

This oath was imposed in March 1534 (Act of Supremacy 1534). The title "Supreme Head" had first been introduced by Henry VIII into a decree of Convocation, 11 February 1531; and had been resisted by the clergy. Though it did not as yet have any religious significance, and might be a matter of compliment only, it might, they feared, receive another interpretation later. But acting under the advice of John Fisher, Warham, and others, they submitted after adding the conditional phrase, quantum per legem Dei licet.

Two years later, the king had broken with the pope, and Parliament had enacted that the king should be "taken, accepted and reputed the only supreme head on Earth of the church of England" by every one of his subjects. But no formula for the oath was laid down in the Act, and great differences seem to have prevailed in practice. Many long "acknowledgments of supremacy" are extant but it would seem that most people were only asked to swear to the Succession, that is to the king's marriage with Anne Boleyn, which the pope condemned, and which therefore involved the supremacy, though the form of the Oath of Succession preserved in The Lords' Journals, refers to the supremacy only lightly. It is unclear what form of the oath Fisher and Thomas More refused to sign. They were ready to accept the succession of Anne Boleyn's children, but refused the supremacy.

The Act of Supremacy was repealed in 1554 by Queen Mary (Second Statute of Repeal) and revived by Elizabeth in 1559 (the Act of Supremacy 1558). The formula then adopted ran:

"I, A.B., do utterly testify and declare in my conscience, that the Queen's Highness is the only supreme Governor of the Realm . . . as well in all Spiritual or Ecclesiastical things or causes as Temporal, &c. &c. &c. So help me God."

This was not to be proposed at once to every one; but was to be taken by the clergy, and by all holding office under the Crown; by others, when asked. This moderation in exacting the oath helped to prevent an outcry against it, and enabled the Government to deal with the recalcitrant in detail. Many years elapsed, for instance, before it was imposed on the graduates of the universities. The last laws passed by Elizabeth against Catholics (1592-3) enjoined a new test for Recusants (Popish Recusants Act 1592). It comprised (1) A confession of "grievous offence against God in contemning her Majesty's Government"; (2) Royal Supremacy; (3) A clause against dispensations and dissimulations, perhaps the first of its sort in oaths of this class.

Elizabeth's "settlement of religion" (see Elizabethan Religious Settlement) had included compromise with the Puritan party, as they were to become, and they were not in love with the supremacy. An informal test was used, asking the suspected person whether he would fight against the pope, if he sent an army to restore Catholicism. The Catholics called this the "bloody question". There was no law to enforce an answer and no specific penalty for refusal.

Towards the end of Elizabeth's reign, a split began in the Catholic ranks on this subject. Some of the priests who had joined in the Archpriest Controversy and appeal against the archpriest George Blackwell had afterwards presented to Elizabeth a "Protestation of Allegiance". This was not the first example of such a declaration of loyalty, but it was the first which withheld from the pope any possible exercise of the deposing power, rather than simply denying the validity of the deposition pronounced by Pius V.