後 in the following sentence doesn't mean "at a later time" but it means "what's left to do", right?
後は契約の署名が残っています。

Question

Answer

Yes,  「後は」 means "the rest" and so here by 「後は～残っています」 would mean as you said "what's left to do" 「他（ほか）にすることは」
So the sentence could be restated as 「他にすることは、署名だけです」