This can be done by doing the following:
  1. Go to Setup -> Receipt Manager
  2. Select the receipt(s) that you want to control
  3. Edit the receipt
  4. Go to Step 7: Minimum Amount (Sets the minimum tax deductible amount required to automatically generate a receipt (An Admin can always generate a receipt for donations below the minimum amount.)
  5. Save
Going forward a receipt will not be generated unless it is over the minimum amount.