Some service industries like restaurants, work on four-week month and not monthly cycles. They need a way to run reports that match their business plans, which require a 13 period (month) tax year reporting.
Setting up 4-week accounting periods:
Four week Profit and Loss reports actually is relatively easy, but each one must be manually created. Unlike the QuickBooks Desktop default report periods that you access from the "drop down" list when creating financial reports, you will need to create each of your 4-week P&L periods individually and then name and save each one using the QuickBooks Desktop Memorize Reports feature.
You should first prepare a list of the beginning and end dates for each of your 13 4-week periods. This will make the process of creating, naming, and saving each one easy.
Creating a 4-week Profit & Loss Report:
Quick Tip: If you want to be able to create a Profit & Loss report that shows comparative 4-week periods side by side for a defined time period in the same report (e.g. This Fiscal Year), then you have to start each of your 4-week periods on a Sunday (and therefore end each period on a Saturday).
Notes: While the typical restaurant week runs Monday-Sunday, QB will not create detailed 4-week reports except in the Sun-Sat format (one of just a few inherent limitation discovered using QB for restaurants).