Reversed Splits are not common but they can happen. Below are the steps to take in order to ensure both monetary totals and compliance reports are correct.
If the original transaction with the splits has not already been added, add them as they originally happened prior to any refunds or returns.
If you only received a refund for one of the splits, navigate to that entity's record and locate the transaction in question. Next, click on the transaction to edit it. Towards the top, click the box for Is Reversal.
Once you've taken those steps, click the Save button to save the split transaction as a reversed split.