could invoice
Regular verb: invoice - invoiced- invoiced

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could invoice
you could invoice
he could invoice
we could invoice
you could invoice
they could invoice 	I could be invoicing
you could be invoicing
he could be invoicing
we could be invoicing
you could be invoicing
they could be invoicing	I could have invoiced
you could have invoiced
he could have invoiced
we could have invoiced
you could have invoiced
they could have invoiced	I could have been invoicing
you could have been invoicing
he could have been invoicing
we could have been invoicing
you could have been invoicing
they could have been invoicing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't invoice
you couldn't invoice
he couldn't invoice
we couldn't invoice
you couldn't invoice
they couldn't invoice 	I couldn't be invoicing
you couldn't be invoicing
he couldn't be invoicing
we couldn't be invoicing
you couldn't be invoicing
they couldn't be invoicing	I couldn't have invoiced
you couldn't have invoiced
he couldn't have invoiced
we couldn't have invoiced
you couldn't have invoiced
they couldn't have invoiced	I couldn't have been invoicing
you couldn't have been invoicing
he couldn't have been invoicing
we couldn't have been invoicing
you couldn't have been invoicing
they couldn't have been invoicing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I invoice?
could you invoice?
could he invoice?
could we invoice?
could you invoice?
could they invoice? 	could I be invoicing?
could you be invoicing?
could he be invoicing?
could we be invoicing?
could you be invoicing?
could they be invoicing? 	could I have invoiced?
could you have invoiced?
could he have invoiced?
could we have invoiced?
could you have invoiced?
could they have invoiced? 	could I have been invoicing?
could you have been invoicing?
could he have been invoicing?
could we have been invoicing?
could you have been invoicing?
could they have been invoicing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I invoice?
couldn't you invoice?
couldn't he invoice?
couldn't we invoice?
couldn't you invoice?
couldn't they invoice? 	couldn't I be invoicing?
couldn't you be invoicing?
couldn't he be invoicing?
couldn't we be invoicing?
couldn't you be invoicing?
couldn't they be invoicing? 	couldn't I have invoiced?
couldn't you have invoiced?
couldn't he have invoiced?
couldn't we have invoiced?
couldn't you have invoiced?
couldn't they have invoiced? 	couldn't I have been invoicing?
couldn't you have been invoicing?
couldn't he have been invoicing?
couldn't we have been invoicing?
couldn't you have been invoicing?
couldn't they have been invoicing?