You don't necessarily need any documents to copy a key, but it depends on the locksmith you use. Most locksmiths will require some form of identification before breaking into a property, but they’re less likely to ask if they’re simply copying a key. Locksmiths will charge a fee for key duplication services. The average locksmith charges for key duplication ranges from £5 to £25 per key, depending on the type of key and the locksmith's fee structure. So if you want a key copied, be sure to shop around for the best price!