When I don't pay my 50gb icloud monthly plan

If your data in iCloud exceed the storage plan you paid for, iCloud will stop working for you. DOn't risk anything. if you are in danger of using unpaid iCloud storage, remove all documents and data that are important for you from iCloud and keep them safe on on a local disk. reduce the amount of iCloud storage to the free 5GB you can use without paying. This way email, iCloud backups and other syncing services will continue to work.

See: iCloud storage upgrades and downgrades - Apple Support

You can decrease your iCloud storage from your iPhone, iPad, iPod touch, Mac, or PC. The downgrade will take effect after your current monthly or annual subscription ends.

If you downgrade your storage plan and your content exceeds the storage you have available, new photos and videos won't upload to iCloud Photo Library and your devices stop backing up to iCloud. iCloud Drive and the other apps that you use with iCloud won’t update across your devices. You can't send or receive messages with your iCloud email address. Learn how to manage your storage by deleting backups, documents, photos, and email messages that you don't need anymore.

If you cancel your plan or you don't renew it, you'll automatically go back to 5GB of free storage.

You will be provided with ample warnings to upgrade your storage before which your files will be removed.

Then what happens to the files? I assume if you don't pay for the extra storage, Apple wouldn't allow the files to remain there. I'm also assuming the files will be deleted. Correct me if I'm wrong.

That information has never been posted.

I don't think that is true, if you don't pay you don't have the storage, safest to assume that happens at once.

The files will be deleted, the only grey area is how long after you stop paying for them to be stored. I always assume immediately, that way I am never disappointed.

Okay, gotcha, thanks!

I have to agree with Csound1. If you stop paying for the storage you should assume your files will be gone the moment it cannot be renewed.

There may be tolerance time before this happens, but since no time frame is given by Apple there should be no expectation of it.

If the payment cannot be made to continue the service expect all files to be removed, and I would not expect any warning be given before deletion occurs, other than the regular "Plan could not be renewed" warning when renewal is attempted but fails.