How to set all user's plan expiration to the same date

I use CBSubs to manage dues for a small user professional (~100) group. Over time some of the members will pay their dues late, which then become a headache to manage the expirations and reminders for payment in the next due date cycle.

I would like to align all Members to have a due date of 8/31/2019. Is there a way to manually force a dues date for a whole CB group for a specific subs plan?

Thanks in advance for your help.

If the membership is yearly I suggest using a "This calendar year" duration then set the "Start date of calendar year" to "09-01" so they all start their subscription "09-01" and end it "08-31" every year no matter when they subscribe.

That is precisely how I have it configured. The problem is that if they pay late or early, there are times where the payment cycle get's off-sync on certain users. Then CB will send out past due notices when they are not really past due. I think it will all work if I can get all the member's accounts to the same due date and then leave it alone.

Can I manipulate the due date somehow?

It's impossible for them to be off sync using a "This calendar year" duration. Every users subscribed to that plan will have the same subscription and expiration date. I'm guessing your notification issues maybe a configuration issue in CBSubs Mailer? If using a mailer for past due notifications please provide how you have it configured.