Up to and including 2017, the lowest corporate tax bracket is:
$0 to $50,000 15%
Does that remain in 2018 with the new law, or is the tax rate now completely flat at 21%?

Federal tax rates on corporate taxable income vary from 15% to 35% until this year of Dec 31st, 2017. However, starting Jan 1st 2018, the effective corporate tax rate will be a flat 21% due to the passage of the Tax Cuts and Jobs Act. State and local taxes and rules vary by jurisdiction, though many are based on federal concepts and definitions. Taxable income may differ from book income both as to timing of income and tax deductions and as to what is taxable. Corps are also subject to a federal AMT and alternative state taxes.On Dec. 20th 2017, the US Senate and House of Representatives passed the Tax Cut and Jobs Act, setting a flat and effective corporate tax rate of 21% on all businesses starting January 1st, 2018 effectively. The Act permanently reduces the corporate tax rate to 21%. A number of deductions and credits are eliminated to broaden the tax base. NOLs are permitted ,beginning in 2018, only to the extent of 80% of taxable income, and NOLs may only be carried forward with limited exceptions for certain farming losses. the research and development credit remains in place to incentivize U.S. development of intellectual property. The corporate AMT is repealed in an effort to simplify the tax law.

Thank you Wnhough for the quick reply.
Bummer. That means a 6% increase for a very small business that was only paying 15%.