7.173  Each House of Parliament is guardian of its own privileges. It alone may invoke them. Until it does so, the other House is free to act as it thinks fit. It follows that, with regard to Commons financial privilege, the Lords may properly make amendments to Commons bills (other than supply bills) which, when they come to be considered by the Commons, are deemed by them to infringe their financial privileges. It also follows that the Lords need not anticipate what view the Commons may take of any Lords amendments with respect to Commons financial privilege. The only exceptions are amendments which prima facie are material and intolerable infringements of privilege, in that they either offend Commons SO 78(3)[306] or impose a charge not authorised by a Ways and Means resolution, and which will be summarily rejected by the Commons unless they have previously passed a supplementary financial resolution. Unless there is reason to believe that the necessary supplementary financial resolution will be made by the Commons, it is unprofitable for the Lords to make amendments of this kind. When such Lords amendments are considered by the Commons:

(i) in the case of an infringement of Commons SO 78(3), the amendment is deemed to have been disagreed to without debate and without Question put;

(ii) in the case of a Lords amendment imposing a charge upon the people which has not been authorised by a Ways and Means resolution, the Speaker calls upon the Member of the Commons in charge of the bill to move to disagree with the Lords amendment forthwith.

7.174  With these exceptions, the Commons may either invoke their financial privileges in respect of Lords amendments or waive them; and the Commons regularly accept Lords amendments which have financial implications. The Speaker of the Commons directs that a "special entry" be made in their Journals implicitly asserting their general rights but stating that the Commons accept the Lords amendment, "the Commons being willing to waive their privileges".

Privilege reasons

7.175  If the Commons disagree to a Lords amendment that infringes their financial privileges, the disagreement is made on the ground of privilege alone, and not on the merits of the amendment, even though the Commons may have debated the merits. The Commons communicate in their message to the Lords that the amendment involves a charge upon public funds or a charge by way of national or local taxation or that it in some other way deals with financial arrangements made by the Commons; and they add words to the effect that the Commons do not offer any further reason, trusting that the reason given may be deemed sufficient. In such cases the Lords do not insist on their amendment. But they may offer amendments in lieu of amendments which have been disagreed to by the Commons on the ground of privilege.

7.176  If the Commons disagree to a Lords amendment which appears to have financial implications but offer an amendment in lieu or an amendment to the words restored to the bill, financial privilege is not at that stage invoked by the Commons and the question whether the Lords amendment infringes privilege does not arise. It is therefore open to the Lords to disagree to the Commons amendment in lieu and to insist on the original Lords amendment, which is then returned with the bill to the Commons for further consideration by them.