0845 numbers are classified as "Special Services: Basic Rate" numbers.
They are often referred to as "local rate" numbers, but since 2004, there has been no "local rate", so this description is obsolete.
They are billed at the same rate as calls to 01 and 02 numbers.
When an 0845 number is called, the call recipient receives a small share of the call cost.
Many telecoms companies now include calls to 0845 and 0870 numbers in bundled call allowances.
Beware when calling from mobiles, as charges for dialling 0845 numbers can be significantly higher - up to 41p per minute.
Here are some links to major telecoms companies, so you can check the tariff that applies to you:
0845 numbers can begin as follows:
The correct way to write telephone numbers beginning 0845 is in the format 0845 xxx xxxx