There's a curious - some would say quaint - Latin phrase some insurance professionals use to spell it out the relationship between insurer and insured. That phrase is uberrimae fidei and it means "utmost good faith". Quite simply, it means that the partnership is founded on both parties being totally honest with each other and not telling any untruths - by commission or omission. In short, it's the reason you don't lie on your own car insurance applications.Whether quaint or otherwise, this idea of utmost good faith is indeed central to the principles of the insurance business that it lies in the centre of each insurance contract. In the lack of such honesty, the contract itself can be null and void. What this means, needless to say, is that unless you tell the truth on your own auto insurance proposal forms, the insurance could be declared invalid. Despite the fact that you've been paying the premiums every month, if the insurer can show you've acted in anything significantly less than utmost good faith, with regards to making a claim, the policy could be declared invalid and you find that you are uninsured.This is a thing that could leave you not only seriously out of pocket, if you have to fund all repairs and damage yourself, but could also put you in serious breach of the law by driving while uninsured. Therefore, the message is pretty clear - don't lie on your own car insurance applications.One of the areas where people seem tempted to be less than truthful pertains to previous motoring convictions. They quite rightly recognise that past infractions will be considered by the insurer when calculating the risks, potentially leading to an increased premium due to this fact. In try to avoid paying the bigger premium, some people might be tempted simply to lie, or not to divulge the entire truth about their motoring convictions. In case of an accident, especially someone to which the police are called and something involving a subsequent summons to court, it's likely that the driver's record will come out. With this thought, there's a risk of the insurance provider then declaring that the insurance policy is actually invalid.Some applicants for auto insurance cover are occasionally economic with the truth when assessing the state of their health insurance and their fitness to operate a vehicle. If the car insurance application form requests any kind of medical declaration as to your fitness to operate a vehicle, it could be extremely short sighted once more to lie about any of it. Still worse, needless to say, is to have told the same lies or to have exercised the same deceit with the Driver and Vehicle Licensing Authority (DVLA) in order to secure or keep your driving licence. This is the criminal offence, your driving licence will be invalid and, alongside it, will be any insurance you had arranged.When it arrived at car insurance applications it's best to be completely honest about modified vehicles. Modifications - especially the ones that alter the performance of the automobile - are key to the insurer's assessment of the risk of insuring the automobile. If they feel they've been misled, or lied to, the probabilities are that they'll consider whether to honour the insurance contract in its entirety.Jon McGovern is from Tescocompare.com [1], the insurance comparison site where you could compare auto insurance [2] policy features and prices.