could bill
Verbo regular: bill - billed- billed

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could bill
you could bill
he could bill
we could bill
you could bill
they could bill 	I could be billing
you could be billing
he could be billing
we could be billing
you could be billing
they could be billing	I could have billed
you could have billed
he could have billed
we could have billed
you could have billed
they could have billed	I could have been billing
you could have been billing
he could have been billing
we could have been billing
you could have been billing
they could have been billing	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I couldn't bill
you couldn't bill
he couldn't bill
we couldn't bill
you couldn't bill
they couldn't bill 	I couldn't be billing
you couldn't be billing
he couldn't be billing
we couldn't be billing
you couldn't be billing
they couldn't be billing	I couldn't have billed
you couldn't have billed
he couldn't have billed
we couldn't have billed
you couldn't have billed
they couldn't have billed	I couldn't have been billing
you couldn't have been billing
he couldn't have been billing
we couldn't have been billing
you couldn't have been billing
they couldn't have been billing	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I bill?
could you bill?
could he bill?
could we bill?
could you bill?
could they bill? 	could I be billing?
could you be billing?
could he be billing?
could we be billing?
could you be billing?
could they be billing? 	could I have billed?
could you have billed?
could he have billed?
could we have billed?
could you have billed?
could they have billed? 	could I have been billing?
could you have been billing?
could he have been billing?
could we have been billing?
could you have been billing?
could they have been billing? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
couldn't I bill?
couldn't you bill?
couldn't he bill?
couldn't we bill?
couldn't you bill?
couldn't they bill? 	couldn't I be billing?
couldn't you be billing?
couldn't he be billing?
couldn't we be billing?
couldn't you be billing?
couldn't they be billing? 	couldn't I have billed?
couldn't you have billed?
couldn't he have billed?
couldn't we have billed?
couldn't you have billed?
couldn't they have billed? 	couldn't I have been billing?
couldn't you have been billing?
couldn't he have been billing?
couldn't we have been billing?
couldn't you have been billing?
couldn't they have been billing?