Single location employer is adopting a new plan and applying for a determination letter. Under Treas Regs 1.7476-2, the notice to interested parties allows for this notice to be posted in a place which is 'customarily used for employer notices to employees with regard to employment and employee benefit matters'.

Anyone know how long this notice must remain on the wall in the break room, so to speak??

Absent anything more on point, I would go with the 2 week period that's not less than 7 days nor more than 21 days prior to IRS receipt of the application. The reg somewhere specifies same as when to post the notice.