As it does each year, CBO, in conjunction with the staff of the Joint Committee on Taxation (JCT), will analyze the President's proposed budget—in this case the FY 2014 Budget—projecting the revenues that will be collected and the spending that will occur over the next 10 years if the President's proposals are adopted. That analysis will incorporate CBO's most recent economic forecast, which was released in February, its projections of how various programs will operate under current law, and its estimates of the budgetary impact of proposed policy changes. It will include estimates—prepared by JCT—of the revenue effects of proposed changes in the tax code.
At the same time, CBO will update its 10-year projections of revenues and spending under current law (its "baseline" projections), to reflect new information obtained since it last issued such projections in February in The Budget and Economic Outlook: Fiscal Years 2013 to 2023.
Those two reports—released a few days apart—will be available in mid-May.