could backdate
Regular verb: backdate - backdated- backdated

Affirmation 	
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I could backdate
you could backdate
he could backdate
we could backdate
you could backdate
they could backdate 	I could be backdating
you could be backdating
he could be backdating
we could be backdating
you could be backdating
they could be backdating	I could have backdated
you could have backdated
he could have backdated
we could have backdated
you could have backdated
they could have backdated	I could have been backdating
you could have been backdating
he could have been backdating
we could have been backdating
you could have been backdating
they could have been backdating	

Negation 	
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I could not backdate
you could not backdate
he could not backdate
we could not backdate
you could not backdate
they could not backdate 	I could not be backdating
you could not be backdating
he could not be backdating
we could not be backdating
you could not be backdating
they could not be backdating	I could not have backdated
you could not have backdated
he could not have backdated
we could not have backdated
you could not have backdated
they could not have backdated	I could not have been backdating
you could not have been backdating
he could not have been backdating
we could not have been backdating
you could not have been backdating
they could not have been backdating	

Interrogative form 	
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could I backdate?
could you backdate?
could he backdate?
could we backdate?
could you backdate?
could they backdate? 	could I be backdating?
could you be backdating?
could he be backdating?
could we be backdating?
could you be backdating?
could they be backdating? 	could I have backdated?
could you have backdated?
could he have backdated?
could we have backdated?
could you have backdated?
could they have backdated? 	could I have been backdating?
could you have been backdating?
could he have been backdating?
could we have been backdating?
could you have been backdating?
could they have been backdating? 	

Interro-negative form 	
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could I not backdate?
could you not backdate?
could he not backdate?
could we not backdate?
could you not backdate?
could they not backdate? 	could I not be backdating?
could you not be backdating?
could he not be backdating?
could we not be backdating?
could you not be backdating?
could they not be backdating? 	could I not have backdated?
could you not have backdated?
could he not have backdated?
could we not have backdated?
could you not have backdated?
could they not have backdated? 	could I not have been backdating?
could you not have been backdating?
could he not have been backdating?
could we not have been backdating?
could you not have been backdating?
could they not have been backdating?