Modals chart

	+	--	Past
Necessity/obligation	Have to Have got to Must		Had to
Prohibition		Must not
Expectation	Is/are supposed to	Is/are not supposed to	Was/were not supposed to
Advice	Should Ought to	Shouldn’t Ought not to	Should or shouldn’t have + past participle Ought to or ought not to have+ part participle
Strong advice/warning with a consequence	Had better	Had better not	*
Suggestion/possibility	Could Might Let’s + SV Why don’t you + SV		Could have  + past participle
Lack of necessity		Don’t have to	Didn’t have to