dead·line
–noun
1. the time by which something must be finished or submitted; the latest time for finishing something.
2. a line or limit that must not be passed.
http://dictionary.reference.com/browse/deadline
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My
If you don't meet a deadline... even if you only miss it by a couple of _seconds_, you haven't lived up to your end of the deal, and the deal is off the table. It doesn't matter how much work you put into it or what personal problems you've endured. You failed to live up to your end of the deal, and, at that point, the deal is _only_ extended at the pleasure of the other party.
Quantum-X doesn't seem to want the late goods, and he has every right to refuse paying for them, provided he's also refusing to receive them... which it also seems he is.
So, that settled, there's the (what's now a) separate matter of the money that's already exchanged hands.
Insofar as I see it, your only real recourses here are to either provide him with the file he's requesting (the "I already gave it to you once" argument is kinda asinine, I think... (hopefully, you see it, too now that you (again, hopefully) understand what a "deadline" is).... and only speaks to a severe lack of customer service skills - especially considering you have copies on-hand), or satisfy the situation by giving him back all monies he's given you for the associated project, thereby terminating all current relations.
But, then what the hell do I know about running your business?
Again... only my