On December 22, 2017, the Tax Cuts and Jobs Act (P.L. 115-97) was signed into law with most of it starting to be effective just ten days later. Give the roughly 115 changes in the law, that was a lot of work for the IRS to issue guidance on which is likely to take many years (we are still waiting for some guidance on the Tax Reform Act of 1986). It's also a lot for taxpayers and tax professionals to deal with.