Which one of these sentences is correct?
The contract will not be signed until you have checked the manuscript and confirmed that everything is ok.
The contract will not be signed until you have checked the manuscript and confirm that everything is ok.
Either one could be correct:
The contract will not be signed until you have checked the manuscript and [have] confirmed that everything is ok.
or
The contract will not be signed until you have checked the manuscript and [then/thereafter] confirm that everything is ok.
I would say they could even be used interchangeably. The distinction in meaning from use of one tense or the other is negligible. Given that both things have to happen before the contract is signed, and that confirming would happen near immediately following checking, it makes no difference whether one says "check and confirm, and then we'll sign" or "check, then confirm, then we'll sign".
I think the correct one is the first one. The sentence is talking about either a past event f a future one. In both cases you don't use present tense
It seems to lack parallel structure. Perhaps a better way to write this would be:
The contract will not be signed until the manuscript is checked and everything is confirmed to be ok.
