Many business firms have  casual days  for office attire.
( ( Many ( business firms ) ) ( ( have ( ( casual days ) ( for ( office attire ) ) ) ) . ) )
(ROOT (S (NP (JJ Many) (NN business) (NNS firms)) (VP (VBP have) (NP (NP (JJ casual) (NNS days)) (PP (IN for) (NP (NN office) (NN attire))))) (. .)))
Business firms have casual days where formal wear is not required.
( ( Business firms ) ( ( have ( ( casual days ) ( where ( ( formal wear ) ( ( is not ) required ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Business) (NNS firms)) (VP (VBP have) (NP (NP (JJ casual) (NNS days)) (SBAR (WHADVP (WRB where)) (S (NP (JJ formal) (NN wear)) (VP (VBZ is) (RB not) (VP (VBN required))))))) (. .)))