When you have a bounced check in 360Members, you need to go back into your offering batch and delete the offering record in question. To do this, go into the offerings section, and set the date for the date this check was given on by clicking on the date in the top left corner of the page and setting the date in both the beginning and ending parts of the range. This should pull up only the offerings from that day. Then, find the offering record for that bounced check, and click on the date of the check under the date column header. This will take you back into the offering batch.
Once you are in the offering batch, find the offering in question again, and to the far right side of the window, you may notice some gray circles with a minus symbol in it. Hover your mouse over it, and it will turn red. If you click on it, this will ask if you want to delete that record. Choose to delete it, and it will be removed from the batch.
When you are finished making the change, if you use Church360 Ledger at your church, make sure to let the person who runs that to adjust the deposit accordingly if they've already posted the deposit from that offering batch.