5 CFR § 3101.104 - Outside employment.
(a) General requirement for prior approval. All Department of the Treasury employees shall obtain prior written approval before engaging in any outside employment or business activities, with or without compensation, except to the extent that the employing bureau issues an instruction or manual issuance pursuant to paragraph (b) of this section exempting an activity or class of activities from this requirement. Approval shall be granted only on a determination that the employment or activity is not expected to involve conduct prohibited by statute, part 2635 of this title, or any provision of this part.
Employees of the IRS, Legal Division, and OCC are subject to additional limitations on outside employment and activities that are set out in bureau-specific rules contained in this part.
(b) Bureau responsibilities. Each bureau, which for the purposes of this section includes the Departmental Offices and the Office of the Inspector General, shall issue instructions or manual issuances governing the submission of requests for approval of outside employment or business activities and designating appropriate officials to act on such requests. The instructions or manual issuances may exempt categories of employment or activities from the prior approval requirement based on a determination that employment or activities within those categories would generally be approved and are not likely to involve conduct prohibited by statute, part 2635 of this title or any provision of this part. Bureaus may include in their instructions or issuances examples of outside employment or activities that are permissible or impermissible consistent with this part and part 2635 of this title. Bureaus shall retain in employees' Official Personnel Folders (temporary side) all requests for approval whether granted or denied.