Clayton is having trouble with Quickbooks on macOS Big Sur. Leo says that he thinks that Quickbooks doesn't support BigSur with older versions of their app. But this technote says they plan to update Quickbooks in the next few weeks. Likely to handle security features required in BigSur. Keep track of it on their blog.
But Leo adds that what they really want to do is update and subscribe to a monthly service. It's much better to get paid every month than once every few years. This way they can keep one's app updated with new features year-round. It's the latest trend.
There are alternatives like Zoho Books.