If you are making a deposit into your personal or business account for more than $10,000, you must immediately report this to the Internal Revenue Service. It doesn't matter if the money is from a parent, proceeds for selling a used car or a loan from a friend for a business. While you might not have to pay taxes on the large cash deposit, you will most certainly be subject to federal penalties and, possibly, money-laundering charges if you don't properly report the deposit.
Make the deposit into the account and ask the bank representative for Form 8300. The bank is required to report the transaction and will report any series of cash deposits that appear to be part of the same transaction in excess of $10,000. Selling your car for $15,000 and making three deposits of $5,000 will lead to bank reporting.
File Form 8300 with the IRS by the 15th day after you complete the transaction. If you sell the car on May 1, you must file Form 8300 by May 16.
Talk to your tax adviser regarding the taxation of the funds. Certain deposits, such as loans and gifts under $13,000, are not taxable. If the money is considered part of income, it will be added to your annual gross income.
Pay taxes associated with the deposit when filing your tax return.