As a manager or board member, can i edit the date of a payment that has already been posted?

Yes, when posting a payment that was received but not posted "in time", you can post the payment on a unit and then click on the date of the payment in the billing history and edit the date of the payment to show in the notes that the payment was actually received and should have been posted on a particular date from the past. Example: A manager receives a check for an owner due payment that was due on May 1st. The owner sent the check in the mail and the check sat in the mailbox until May 3rd which is 2 days past the day it was due. The manager of the HOA would then posted the check payment to the owner's unit account on May 3rd and then after the check payment has posted, they need to click on the date of the payment from the unit billing history and edit the payment date to be May 1st. Note: this will not erase of get rid of any late fees that may/may not have posted to the owners unit billing history.