could tier
Regular verb: tier - tiered- tiered

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could tier
you could tier
he could tier
we could tier
you could tier
they could tier 	I could be tiering
you could be tiering
he could be tiering
we could be tiering
you could be tiering
they could be tiering	I could have tiered
you could have tiered
he could have tiered
we could have tiered
you could have tiered
they could have tiered	I could have been tiering
you could have been tiering
he could have been tiering
we could have been tiering
you could have been tiering
they could have been tiering	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't tier
you couldn't tier
he couldn't tier
we couldn't tier
you couldn't tier
they couldn't tier 	I couldn't be tiering
you couldn't be tiering
he couldn't be tiering
we couldn't be tiering
you couldn't be tiering
they couldn't be tiering	I couldn't have tiered
you couldn't have tiered
he couldn't have tiered
we couldn't have tiered
you couldn't have tiered
they couldn't have tiered	I couldn't have been tiering
you couldn't have been tiering
he couldn't have been tiering
we couldn't have been tiering
you couldn't have been tiering
they couldn't have been tiering	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I tier?
could you tier?
could he tier?
could we tier?
could you tier?
could they tier? 	could I be tiering?
could you be tiering?
could he be tiering?
could we be tiering?
could you be tiering?
could they be tiering? 	could I have tiered?
could you have tiered?
could he have tiered?
could we have tiered?
could you have tiered?
could they have tiered? 	could I have been tiering?
could you have been tiering?
could he have been tiering?
could we have been tiering?
could you have been tiering?
could they have been tiering? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I tier?
couldn't you tier?
couldn't he tier?
couldn't we tier?
couldn't you tier?
couldn't they tier? 	couldn't I be tiering?
couldn't you be tiering?
couldn't he be tiering?
couldn't we be tiering?
couldn't you be tiering?
couldn't they be tiering? 	couldn't I have tiered?
couldn't you have tiered?
couldn't he have tiered?
couldn't we have tiered?
couldn't you have tiered?
couldn't they have tiered? 	couldn't I have been tiering?
couldn't you have been tiering?
couldn't he have been tiering?
couldn't we have been tiering?
couldn't you have been tiering?
couldn't they have been tiering?