"Audit Technique Guides (ATG) (also know as MSSP Guides) . . . provide auditing techniques, assist with issue identification and development, and tax law interpretation. Audit Technique Guides are available to the public and can be accessed a thttp://www.irs.gov/Businesses/Small-Businesses- & -Self-Employed/Audit-Techniques-Guides-ATGs." IRM 18.104.22.168.15
"(1) The objective of an ATG is to capture a unique business practice of a particular segment or issue studied. (2) The intent of an ATG is to provide examination techniques found to be useful when examining a unique business practice, but does not provide legal analysis or resolve positions on controversial or unusual legal issues. (3) The Retail Industry Audit Technique Guide can be accessed at: http://www.irs.gov/pub/irs-mssp/retail_industry_102005_final.pdf." IRM 22.214.171.124.12
Below is a pertinent abbreviation.
Below are links to select sources offering field service advice.