The Electoral Commission informs me that it considered the workability of these provisions when the Political Parties and Elections Bill was before Parliament, and set out its views in its briefing notes at that time. The notes are available on the Commission's website:
and copies have been placed in the House of Commons Library.
In summary, the Commission's view was that the provisions finally incorporated in the Act addressed some of its concerns about previous amendments. In particular, the provisions clarified the obligations of those receiving donations that require a declaration from the donor about tax status. However, the Commission said that it would be helpful if the Government could explain the steps that recipients should take if they doubt the accuracy of a declaration, and clarify how donations should be aggregated for the purpose of establishing whether a declaration is required.
In terms of enforcement of the new provisions, the Commission informs me that it would expect to pass on any allegation that an individual had made a false declaration about their tax status to the police or another appropriate authority.