Your five-digit membership / WWOOF ID number will be listed towards the top of either the 'receipt' or 'invoice' email you get when you join WWOOF UK. You can also find it by logging in - it is listed on the left-hand side of the screen under "Membership". If you are a book member, you will see your ID number both on the letter that accompanies the book and highlighted on the envelope you receive your book in. You will need to quote this ID number when you first contact hosts, in order that they can check in advance if your membership number is valid. This computerised ID check has replaced the old system of giving WWOOFers membership cards because cards were often forgotten/lost. Also, hosts were previously unable to check a volunteer's membership status before their arrival.