The difference between not-for-profit and tax-exempt is: one is a term relating to state law, while one is a tax term.
In June the IRS released a lengthy list of not-for-profits that lost tax-exempt status for not filing a Form 990 for 3 straight years. Luckily, many of those not-for-profits may be able to get their tax-exempt status back by following an IRS procedure. The IRS explains more in this YouTube video.
Earlier this month, the IRS released the names of organizations that have lost tax-exempt status for failing to file a Form 990 with the IRS for 3 straight years. The IRS also released a Revenue Procedure that offers guidance on how these organizations can regain tax-exempt status. This link takes you to a page on IRS [...]