title: Database design: Custom fee/billing charge rates
body: <p>A user can have custom billing rates, which may differ from one user to another.</p>
  
  <p>You would most likely have a default billing fee table, that would look something like this</p>
  
  <pre><code>FEE
  Id
  FeeTypeId
  FixedCharge
  VariableCharge
  </code></pre>
  
  <p>When you charge the customer you might send them an invoice etc and then you have a  table that stores the billed/charge amount that might look like this!</p>
  
  <pre><code>USER_TRANSACTION_CHARGE
  Id
  UserId
  FeeId
  ChargeName
  ChargeAmount
  DateTime
  </code></pre>
  
  <p><strong>How do you design it for custom billing rates per specific user?</strong></p>