2 U.S.C. § 642: Budget-related legislation must be within appropriate levels

the enactment of that bill or resolution as reported; the adoption and enactment of that amendment; or the enactment of that bill or resolution in the form recommended in that conference report; would cause the level of total new budget authority or total outlays set forth for the first fiscal year in the applicable resolution to be exceeded; or would cause revenues to be less than the level of total revenues set forth for that first fiscal year or for the total of that first fiscal year and the ensuing fiscal years in the applicable resolution for which allocations are provided under section 633(a) of this title . After a concurrent resolution on the budget is agreed to, it shall not be in order in the Senate to consider any bill, joint resolution, amendment, motion, or conference report that would cause a decrease in social security surpluses or an increase in social security deficits relative to the levels set forth in the applicable resolution for the first fiscal year or for the total of that fiscal year and the ensuing fiscal years for which allocations are provided under section 633(a) of this title . For purposes of subsection (a)(3), social security surpluses equal the excess of social security revenues over social security outlays in a fiscal year or years with such an excess and social security deficits equal the excess of social security outlays over social security revenues in a fiscal year or years with such an excess. For purposes of subsection (a)(3), no provision of any legislation involving a change in chapter 1 of the Internal Revenue Code of 1986 [ 26 U.S.C. 1 et seq.] shall be treated as affecting the amount of social security revenues or outlays unless that provision changes the income tax treatment of social security benefits. the enactment of that bill or resolution as reported; the adoption and enactment of that amendment; or the enactment of that bill or resolution in the form recommended in that conference report;