get (something) over with

To do, finish, or accomplish something—especially that which is difficult, unpleasant, or undesirable—as promptly or quickly as possible so as to no longer have to think about or deal with it. I absolutely hate getting blood drawn, so let's just get in there and get it over with! I'm looking forward to getting my final exams over with so I can relax and enjoy my summer break. I know you want to get this project over with, but slow down and do the work carefully.

get it over with

An exhortation to do something quickly (typically because it is unpleasant). I know you have to draw blood, so go ahead, get it over with! It looks like you have some bad news for me, so just tell me what it is—get it over with. I suspect there are so many errors because he doesn't take his time with the filing—he just wants to get it over with.