When doing back office "offline" membership renewals (cash, cheque, phone) we have recently noticed that when we select "Renew" from the "Active Membership" window the membership dates are updated correctly but the contribution is recorded as 0.00. I just ran a test and created a new member with a cash payment of membership fee and the amount was correctly recorded in contributions at that stage. When I then used "Renew" to renew the membership the corresponding contribution is listed as 0.00. (The amounts in the forms for processing the renewal are correct.)
Rather new to CiviCRM and I apologise if I am missing something obvious, but this has me baffled. Fortunately we are not using CiviCRM for our accounting.
Re:CiviCRM 4.6.15, on Drupal 7