A bill certified by its originating chamber versus the final bill agreed to by both chambers.
If I Can't Have You
A bill must pass in identical form by both the House and the Senate before it can be signed into law by the President (i.e., regular order). An engrossed bill is the official reprinted copy of the final text of a bill incorporating all accepted amendments as passed by a chamber that is then physically transmitted to the other chamber. The House and Senate use different colors to distinguish between their engrossed bills: the House prints on blue paper, and the Senate prints on white paper.
There's Nothing Holdin' Me Back
An enrolled bill is the final version of the measure agreed to by both chambers and submitted to the President for signature. U.S. Code requires a physical copy of the legislation be printed on parchment, a practice that dates to the first years of Congress when it was used to prevent the forgery of legislation. The enrolled bill is signed by the Speaker of the House and President Pro Tempore of the Senate. Preparing and signing enrolled bills can be a long and technical process, especially at the end of a Congress when many are being prepared. From there, the Office of the Federal Register assigns the bill a public law number. The Office of the Law Revision Counsel in the House subsequently classifies the bill in the U.S. Code, and the statute is ultimately printed by the Government Publishing Office.
From time to time, mistakes are made in a final enrolled bill. If this occurs and somehow yields substantive changes to the legislation, the President may issue a signing statement indicating a willingness to follow the intent of the law. To make more substantial changes to an enrolled bill, both chambers of Congress must agree to a concurrent resolution to re-enroll the bill with the specified changes. These technical correction resolutions are typically agreed to in both chambers by unanimous consent. If irregularities in enrollment are not addressed with a new enactment, then the underlying discrepancy could be challenged in federal court. One such example occurred with the Deficit Reduction Act of 2005, when an error in the engrossed text was accidentally agreed to by both chambers. It was corrected without a concurrent resolution, which led to a legal challenge of its constitutionality. A Supreme Court ruling from the 1890s, however, states that the enrolled and signed bill is the letter of the law.