When a Tax Status verification is performed in GIFTS, GIFTS Online, GIFTS Alta, or FIMS, it is checked against the MicroEdge Tax Exempt database.  This MicroEdge Tax Exempt database is updated weekly from the IRS Business Master File (BMF). Please note the IRS updates the BMF on a monthly basis.  Therefore, there can be a delay between when a nonprofit is added or removed from the MicroEdge Tax Exempt database.

Regarding the Automatic Revocation List and the Internal Revenue Bulletins:  
The Automatic Revocation List contains all the nonprofits who lost their status because they failed to file a 990 within the three year limit. This information should be in the BMF but there is a lag in time between when the IRS revokes their status and when they are added to the BMF.  As of March of 2013, organizations that have had their nonprofit status revoked are added to the BMF monthly.    The IRB (Internal Revenue Bulletin) is a weekly document that may contain information about organizations who lost their status for any variety of reasons. This is the list that Guidestar verifies manually.