One of the more valuable HMRC/Tax documents is a P45. Why? Because it is one of the most required documents for job candidates seeking employment in the UK. Standard procedure for any potential new employer is to request that you provide a P45 document as verification of your tax code. If you fail to provide this important document, it just might result in you paying excessive taxes- which, of course, no one wants to do. Having this critical document on hand will save you both money and heartache down the road. Without it, your new employer will most likely have to use an emergency tax code instead of the correct one that is specific to your individual tax situation.