Hi Krystal!
Buyers only get penalized if you as a seller write in, letting us know that a buyer has not paid for their invoice even though you've requested it from them. There's no automatic way that a buyer's account is "marked" if they're late in providing payment. That being said, non payments for purchase orders is grounds for removal on the Wholesale platform, so if a buyer doesn't pay even after you've reached out to them, please don't hesitate to let us know!
An automatic reminder is a great idea, and one that we're aware of as requested by sellers. It's on our list of features to consider for future updates to the platform. We appreciate hearing your feedback, and definitely let us know here, or at wholesalesupport@etsy.com if you have more ideas for us to consider!