In order to use the income for car loan purposes, you would have to have claimed it on your tax returns. Theoretically, you claimed all yout tip income on your returns just as you claim your W2 income – this is required by the IRS. While we understand that many people do not claim their full cash earnings, or even fully inderstand that they are supposed to do so, there is no way to “have your cake and eat it too” – that is, avoid taxation, but still use this income for other purposes, such as car loans.
Talk to your tax preparer. You may be able to correct or amend your past tax filings to reflect your true, corrected income – and pay the taxes. You would then have a record of those earnings in your tax returns. If you dont wish to do that, you must begin claiming all the income in the next year of filing, and build up a 2 year history of having done so, in order to use the income to qualify for a car loan.