Before you stop payment on your check, contact the dealer and try explaining your reasons for having to back out of the deal. Perhaps s/he will make an exception in your case and let you out of your agreement. Be aware, however, that since you signed a contract stating that you understood that your deposit was non-refundable, a dealer is normally under no legal obligation to let you out.

In most cases, if the dealer chooses to enforce your contract terms and you stop payment anyway, you will have violated a legal sales contract and will remain in debt for the deposit payment. If the dealer cares to report this unpaid debt to the credit bureaus, s/he may legally do so.

However, there may be particular laws in your state regarding "buyer's remorse." So, before you do anything else, it might be a good idea to contact your state Attorney General's office and find out what your options may be. This listing can normally be found in your local telephone book.

For general credit information, you might check out "How Should I Handle My Credit to Prepare for the Future?"