QuickBooks stores data pertaining to Customer:Jobs, Vendors, Employees, Other Names, Accounts and Items, as well as other things, in lists. A particular Customer or Employee or Item is an entry on a list. Your lists can become damaged. The damage can often be repaired by re-sorting which puts the list back in its default order.
Re-sorting your lists into their default order can fix a number of data problems, especially when done prior to rebuilding your data file.
When a knowledge base article asks you to re-sort your lists, it is usually asking you to re-sort:
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