should underpin
Regular verb: underpin - underpinned- underpinned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I'd underpin
you'd underpin
he'd underpin
we'd underpin
you'd underpin
they'd underpin 	I'd be underpinning
you'd be underpinning
he'd be underpinning
we'd be underpinning
you'd be underpinning
they'd be underpinning	I should've underpinned
you should've underpinned
he should've underpinned
we should've underpinned
you should've underpinned
they should've underpinned	I should've been underpinning
you should've been underpinning
he should've been underpinning
we should've been underpinning
you should've been underpinning
they should've been underpinning	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I shouldn't underpin
you shouldn't underpin
he shouldn't underpin
we shouldn't underpin
you shouldn't underpin
they shouldn't underpin 	I shouldn't be underpinning
you shouldn't be underpinning
he shouldn't be underpinning
we shouldn't be underpinning
you shouldn't be underpinning
they shouldn't be underpinning	I shouldn't have underpinned
you shouldn't have underpinned
he shouldn't have underpinned
we shouldn't have underpinned
you shouldn't have underpinned
they shouldn't have underpinned	I shouldn't have been underpinning
you shouldn't have been underpinning
he shouldn't have been underpinning
we shouldn't have been underpinning
you shouldn't have been underpinning
they shouldn't have been underpinning	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
should I underpin?
should you underpin?
should he underpin?
should we underpin?
should you underpin?
should they underpin? 	should I be underpinning?
should you be underpinning?
should he be underpinning?
should we be underpinning?
should you be underpinning?
should they be underpinning? 	should I have underpinned?
should you have underpinned?
should he have underpinned?
should we have underpinned?
should you have underpinned?
should they have underpinned? 	should I have been underpinning?
should you have been underpinning?
should he have been underpinning?
should we have been underpinning?
should you have been underpinning?
should they have been underpinning? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
shouldn't I underpin?
shouldn't you underpin?
shouldn't he underpin?
shouldn't we underpin?
shouldn't you underpin?
shouldn't they underpin? 	shouldn't I be underpinning?
shouldn't you be underpinning?
shouldn't he be underpinning?
shouldn't we be underpinning?
shouldn't you be underpinning?
shouldn't they be underpinning? 	shouldn't I have underpinned?
shouldn't you have underpinned?
shouldn't he have underpinned?
shouldn't we have underpinned?
shouldn't you have underpinned?
shouldn't they have underpinned? 	shouldn't I have been underpinning?
shouldn't you have been underpinning?
shouldn't he have been underpinning?
shouldn't we have been underpinning?
shouldn't you have been underpinning?
shouldn't they have been underpinning?