The ITRD and LAS respectively interpret the ITA and assist in applying those interpretations to the audit facts

The Legislative Application Section (LAS) “provides technical assistance to large case auditors in the application of the ITA to specific facts and issues identified in the context of an income tax audit,” whereas the Income Tax Rulings Directorate “focuses on interpretive issues” - but the two consult frequently.

The LAS issues its memoranda directly to the auditor with that memo being distributed at the discretion of the auditor. However, the taxpayer may formally request a severed copy of the memo under the Access to Information procedure or (preferably) informally request a copy.

Neal Armstrong. Summary of May 2015 CPA Roundtable, Plenary Q.2 under s. 152(1).