I have to make several assumptions to answer. With regard to your tax situation, if you are married and are not separated from your wife, then your filing status should normally be Married Filing Jointly. (Separate filing is not normally recommended--especially if you expect to receive tax credits.) Now let's discuss the dependency status for your step-son. This can sometimes be complicated--especially if there is a custody agreement, such as in cases with a divorce. To simplify, I will assume a typical situation where you have full legal custody of the child; your step-son is an unmarried U.S citizen; he is under age 19; you are older than the child; and you provided over half of the child's support. In such a case, to claim your step-son as a dependent, then your step-son must have also lived with you for over half of the year. If he did not live with you for over half of the year, then you cannot normally claim him as your qualifying child for the dependency. (Divorce/separation documents can sometimes modify this.) You would normally just list your step-son on your tax return. Providing proof is not an issue for filing. However, if there are custody or dependency issues with another person, such as his biological parent, who also claims your step-son on their tax return, then that will raise a flag to stop all tax returns that list your step-son. At that point, proof will become and issue, and you would want to have data to substantiate the facts to the IRS. In such cases, the person who is found to have provided false information could receive penalties. So you just need to be honest, and proof is not needed to file.
Now with regard to your car. Do you pay good money and expect your insurance company to be honest to pay your loss if you ever suffer an unfortunate circumstance? If so, please understand that your insurance company expects you to be honest too! You normally certify that all information that you give to your insurance company is truthful and accurate. If your insurance company learns that you willfully lied about the car's location in order to pay them less money than required to cover their risk, then will they have grounds to avoid paying your claim? Don't give the insurance company a way to avoid paying you. Honesty is the best policy, and then you shouldn't have to be "worried".
