You need to bring your driving licence with you when you are hiring a car. This may sound obvious but you would be surprised to know that this is most common mistake made by persons hiring cars.
In the UK in particular there is a new style driving licence which comes in two parts. The first part has your photograph on it. The second part has information about any endorsements or disqualification you may have had in the past. Persons with the new style driving licence often will only take with them the part with the photograph on it. They believe that this will be sufficient to prove that they have a driving licence. However the car rental companies will not accept this part of the driving licence on its own. They need to see the second part of the licence also. They need to establish that you are qualified to drive the vehicle that you are hiring and that you have not been disqualified from driving in the past. If you have for example been convicted in court of driving whilst under the influence of alcohol, they will not normally hire a car to you until a period of 10 years has elapsed without further disqualification.
If you find yourself in the position where you have forgotten either part of your driving licence or you cannot find it, there may be a still a way round that problem. The car rental companies have a facility that allows them to contact the D.V.L.A (Department of Vehicle Licensing Authority). They will phone the D.V.L.A on your behalf and confirm your driving licence is in order. They will charge you a fee for this service normally about GBP 5.00 plus vat.
There can be a problem with using the D.V.L.A option however. The D.V.L.A are only open certain hours on certain days, so the car rental company will not be able to contact them outside these hours. If that is the position then there is no way round it.
If however you know in advance that you will not have your driving licence when you attend to collect your car and that the D.V.L.A will be closed at that time, you can arrange with the car rental company to have the D.V.L.A check carried out prior to your arrival at a time the D.V.L.A is open. The D.V.L.A will not give your personal details to the car rental company without your permission so you would have to phone them in advance and explain the position, giving them your permission to give your information to the car hire company.