(1) On April 1, 2021; or
(2) If related to the definition of taxable income, as applicable to the tax year of the taxpayer. [1969 c.493 §3; 1971 s.s. c.4 §2; 1975 c.672 §3; 1983 c.162 §59; 1985 c.802 §1; 1987 c.293 §2; 1989 c.625 §2; 1991 c.457 §1; 1993 c.726 §27; 1995 c.556 §1; 1997 c.839 §1; 1999 c.224 §7; 2001 c.660 §35; 2003 c.77 §14; 2005 c.519 §9; 2005 c.832 §27; 2007 c.614 §12; 2008 c.45 §13; 2009 c.5 §23; 2009 c.909 §§24,25; 2010 c.82 §§24,25; 2011 c.7 §23; 2012 c.31 §22; 2013 c.377 §22; 2014 c.52 §24; 2015 c.442 §16; 2016 c.33 §19; 2017 c.527 §20; 2018 c.101 §20; 2019 c.319 §20; 2021 c.456 §21]