Within Ecommerce you can perform partial reversals. Partial Reversals are for purchases that includes additional donation. Only the additional donation can be partially reversed.
1. Go to Commerce > Ecommerce 2. Hover over Initiative Name 3. Click Bookkeeping > Manage Initiative Records 4. Search for the purchaser > Click Edit 5. Click Delete Record from Initiative 6. Apply the partial reversal 7. Click Submit Reversal