The biggie is no licence or an inncorrect license. Then all bets are off. What gets me is, none of the insurance companies ask to see any of these documents before they issue a policy, but as soon as you make a claim they want to see them. I find that strange.
Some insurance companies still require a copy of your licence--you can legally drive down to an MOT station for a pre booked MOT without tax or MOT and of course your insurance is valid.
It is an offence to drive an un roadworthy vehicle on the road-if a required bulb fails a minute after your MOT you are driving an non roadworthy vehicle and commiting an offence.
If you do not have a MOT and are involved in a collision you will have to prove your vehicle was roadworthy to get a full payout but you are still covered by insurance.
Your always insured wheter you have tax or not