In order to edit an offline batch which has already been submitted, go to Dashboard > Donations > Offline batches. Click the 'edit' icon to the right of the batch you wish to edit.
To remove a donation entirely, click the '-' icon to the left of the donation in question.
To mark donations as returned, click the arrow icon to the left of the donation in question. This will keep the donation in the system, but will mark it as returned.You can also edit the donor, the donation amount, the fund, or the type of donation.