Taxation (International and Other Provisions) Act 2010 section 3

Arrangements may include retrospective or supplementary provision

Section 3 confirms that double taxation arrangements given effect under section 2 remain valid even where they apply retrospectively, cover income or gains not actually subject to double taxation, or assign decision-making roles to public authorities.

• Arrangements are effective even if they grant tax relief for periods before the Act was passed or before the arrangements themselves were made.
• Arrangements may deal with income, chargeable gains or foreign-field consideration that is not actually subject to double taxation, and they still take effect.
• Arrangements may confer functions on a UK or overseas public authority to determine matters arising under the arrangements.
• "Foreign-field consideration" means amounts charged to petroleum revenue tax under section 12 of the Oil Taxation Act 1983 in respect of UK use of a foreign field asset.