The IRS updates its contingency plan in anticipation of a possible government shutdown.
The IRS annually updates its fiscal year lapsed appropriations contingency plan in anticipation of a possible lapse in funding if Congress fails to pass legislation to continue funding a substantial portion of the government.
Although the unfunded agencies would include the Department of Treasury and IRS, the IRS current plan for FY2025 (updated as of July 22, 2024) notes that the IRS has available multi-year funding under H.R. 5376 (commonly called the “Inflation Reduction Act” (IRA)) and would use that funding for the activities outlined in its plan.
With respect to the Office of Chief Counsel in particular, it appears that some of the employees would be retained despite the lapse in government funding, which could allow the IRS to continue issuing guidance.
Still, many, and perhaps most, other functions would remain unfunded and suspended until Congress and the president reach an agreement on funding. These could include the audit and exam functions and those IRS personnel responsible for fielding and answering taxpayer questions.