State laws and insurance companies' guidelines vary on how payment for damages is processed and the check made out. Some insurers pay the repair shop of your choice directly others make the check out to you and the repair shop or just you alone (as long as you do not have a lien holder).

Before trying to return the check it likely would be easier to get estimates for your repairs and see if any repair or body shop is within the amount you were given. If so then take your vehicle in for repair. If then the mechanic finds extra damage and determines it will cost more than your check amount for the repairs you would contact the insurance company to find out about receiving an additional or supplemental payment to pay for the full repair of your vehicle that was rear-ended.

If additional payment is needed likely the insurance adjuster working your claim will come out to the repair shop to see why the cost is more than he or she believed and had the insurance company cut the check for. If the claims adjuster agrees with the extra costs than a supplemental payment should be made by the insurance company so the total repair is paid for.

So if you find that the repairs will cost more than your original check the insurance company will usually issue a second payment, the first one being the check you already received, as a supplemental payment to cover the difference between the first estimate and the final repair bill.

If you are having problems finding a repair shop that has an estimate anywhere near your check amount for the work that needs to be done or if you just want a referral to a reputable mechanic than you can ask the insurance company if they have any preferred companies they would suggest however in most states the choice of repair shops is up to the car owner and the insurance company cannot tell you to take the car to one specific shop.

Speak to the insurance company involved about your concerns and the best way in which to make sure their payment covers the total cost of repairs and if you want a list of repair shops they would recommend. To find out what your options and consumer rights according to your state laws contact your state's insurance regulator.