new car in cash suspicious to the IRS

Large cash transactions get "recorded", that's basically all. 

If you get audited for your tax, assume they will know about that money, and ask you. If your pay slips, tax returns, bank accounts all show how you legitimately earned the money and paid tax on it, then no worries. 

If you happened to earn the money illegally or "under the table" (not declared on your tax) then you might have some serious explaining to do. 

It's safer and less suspicious to buy the car with a bank check made out to the dealer. The dealer wont even need to know if it's your money, or you have taken out a loan from you bank.

It's not illegal to buy a car with cash, but businesses have to report receipt of large cash payments to IRS. The reportable amount starts at $10,000.01. Buying a car with a check is no problem, so if you have a bank account I'd use that method of payment. Cash if $10,000 or less is OK

Transactions above $10,000 in cash get reported to the IRS. 

The IRS doesn't look into it further unless you are doing them twice a week. 

I suspect you have a few years to go before you get your hand on $10,000. Even then, you could use a check and they don't get reported. 

I have probably been reported a half dozen times over the last 20 years. Ive never worried about it and never will. Because its MY money and Im not doing anything illegal. Im not a terrorist, a drug dealer or a tax cheat. Its not up to me to prove it. they have to prove it.

I hate the irs. I don't put my money in the bank because I don't want them to know. Buy the car with cash, dangle it in their face! Show them you spent money they can't have! It's your money, do what you want! I'm not sure how they'd find out but I guess suppose they do, well.....idk I don't pay taxes of anything so I don't know but my point is, the government and irs wants to take all our money!

You'll be fine but,consider paying for most of it in cash, then make payments for the rest of it over 6 months. You will establish good credit that way, in case you ever DO need it. Btw, a high credit score will get you cheaper insurance,better rental options,maybe even a better job. They shouldn't be allowed to use your credit history that way but they do.So use the system to your advantage.