From Longman Dictionary of Contemporary English
the clock is ticking
used to say that there is not much time left to do something
Hear the example used here:
The Wolf: You’re… Jimmie, right? This is your house?
Jimmie: Sure is.
The Wolf: I’m Winston Wolf. I solve problems.
Jimmie: Good, we got one.
The Wolf: So I heard. May I come in?
Jimmie: Uh, yeah, please do.
The Wolf: You must be Jules, which would make you Vincent. Let’s get down to brass tacks, gentlemen. If I was informed correctly, the clock is ticking, is that right, Jimmie?
Jimmie: Uh, one hundred percent.
The Wolf: Your wife… Bonnie comes home at 9:30 in the AM, is that correct?
The Wolf: I was led to believe that if she comes home and finds us here, she’d wouldn’t appreciate it none too much?
Jimmie: [laughing] She wouldn’t at that.
The Wolf: That gives us exactly… forty minutes to get the fuck out of Dodge. Which, if you do what I say when I say it, should be plenty. Now, you’ve got a corpse in a car, minus a head, in a garage. Take me to it.
The phrase get down to brass tacks (not brass tax) is an Americanism dating from the 19th century. In the idiom, brass tacks means (1) the essentials, or (2) the basic facts, so to get down to brass tacks is to focus on the essentials.
The phrase’s exact derivation is unknown, though there are a few theories. One is that the expression is inspired by the centrality of actual brass tacks in furniture and upholstery. Another is that brass tacks is simply a bit of rhyming wordplay derived from facts. In any case, the phrase was widespread in its modern sense by the early 20th century.