Present perfect or Past tense? Which sentence is correct?

Question

I'm confused. Which sentence is correct?

"You have said you would buy a car if you got driver's licence"

or

"You said you would buy a car if you got driver's license"

or

"You have said you will buy a car if you get driver's license"?

Answer 1

You have said you would buy a car if you got driver's licence

The word "have" could be considered redundant as "said" already denotes past tense, but sometimes when we are referring to a specific instance of someone saying something it becomes idiomatic to say "you have said". For example, if you were reviewing with someone their previously written answer to a question it might be easier to say "you have said..." which tacitly refers to their written answer, than to say "you said in your answer...".

This version of the sentence uses "got", which is the past tense (as opposed to "get"). Again this could be okay if you were referring to somebody's past statement where either you know that the person has subsequently got a driver's license or it remains ambiguous whether or not they have got one in the time that has elapsed since they said it.

You said you would buy a car if you got driver's license.

This sentence is fine. It omits the unnecessary "have". The use of "got" is acceptable if it meets the same condition mentioned in my previous paragraph. You might use either this version or the previous one to review a person's previous statement to either challenge it (becuse they have got a licence but not bought a car) or as a prelude to ask if they have got their licence.

You have said you will buy a car if you get driver's license

Ignoring the word "have" (see my answer to the first statement), this sentence uses "get", which makes the conditional part of the subject's previous statement a future event. This version implies understanding that the person has not yet got a driver's licence, but they have stated that if or when they do, they will buy a car.

Answer 2

They're all syntactically perfectly valid, BUT check out this usage chart...

OP's Present Perfect versions (#1 & #3) are at least slightly "marked". Which is to say they're a bit "unusual", because native speakers normally use simpler tense forms unless there's a compelling reason to complicate things.

Because of that general principle, native speakers tend to look for something slightly unusual about the context and/or intended nuance for versions #1 & #3. For me at least, the first thing that comes to mind is they'd be more likely in some formal legal cross-examination context.

If I knew that wasn't the case, my guess would be the speaker is deliberately using "starchy / formal" phrasing in order to intimidate the addressee. If that's what you wanted to do anyway, then go ahead. But this sort of thing is a risky business for non-native speakers, so my advice would be to stick to simpler tenses wherever possible.

---

As to the would / will choice, it's almost always more common to "backshift" to would in such future and / or hypothetical contexts. Choosing the less common alternative has much the same effect as that described above - with the additional factor that it slightly emphasizes the "real future, not hypothetical possibility" aspect. Which again could be seen as "pressurizing" the addressee to make good on his promise.