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Interpretation Act 1978

Interpretation Act 1978[1]
Act of Parliament
Long titleAn Act to consolidate the Interpretation Act 1889 and certain other enactments relating to the construction and operation of Acts of Parliament and other instruments, with amendments to give effect to recommendations of the Law Commission and the Scottish Law Commission.
Citation1978 c. 30
Royal assent20 July 1978
Commencement1 January 1979[2]
Other legislation
Status: Amended
Text of statute as originally enacted
Revised text of statute as amended
Text of the Interpretation Act 1978 as in force today (including any amendments) within the United Kingdom, from

The Interpretation Act 1978[1] (c. 30) is an act of the Parliament of the United Kingdom. The Act makes provision for the interpretation of Acts of Parliament,[3] Measures of the General Synod of the Church of England, Measures of the Church Assembly,[4] subordinate legislation,[5] "deeds and other instruments and documents",[6] Acts of the Scottish Parliament and instruments made thereunder (added 1998),[7] and Measures and Acts of the National Assembly for Wales and instruments made thereunder.[8] The Act makes provision in relation to: the construction of certain words and phrases, words of enactment, amendment or repeal of Acts in the Session they were passed, judicial notice, commencement, statutory powers and duties, the effect of repeals, and duplicated offences.

The Act repealed the whole of the Interpretation Act 1889, except for sections 13(4) and 13(5) and 13(14) in their application to Northern Ireland.[9]

The Interpretation Act (Northern Ireland) 1954[10] applies in the same way to Acts of the Parliament of Northern Ireland or an Act of the Northern Ireland Assembly.

The Interpretation Act 1978 applies to itself and to any Act passed after the commencement of the Act (section 22) and, to the extent specified in Part I of Schedule 2, to Acts passed before the commencement of the Act.

The Interpretation Act 1978 binds the Crown.[11]

Section 4

This section replaces the corresponding provision of the Acts of Parliament (Commencement) Act 1793. See Coming into force.

Section 5

Section 5 and Schedule 1 provide definitions of certain words and phrases.

Section 6

Unless it is clear there is a contrary intention, wherever in any Act of Parliament or Statutory Instrument there are words importing the masculine gender, the words should be construed to incorporate the feminine and vice versa. Also, words in the singular include the plural, and as with the interchangeability of words importing gender so it is with the plural and singular.[12]

Section 7

This section, concerned with service of documents by post, replaced section 26 of the Interpretation Act 1889.[13] It states that

Where an Act authorises or requires any document to be served by post (whether the expression "serve" or the expression "give" or "send" or any other expression is used) then, unless the contrary intention appears, the service is deemed to be effected by properly addressing, pre-paying and posting a letter containing the document and, unless the contrary is proved, to have been effected at the time at which the letter would be delivered in the ordinary course of post.[14]

Interpretation of the words unless the contrary is proved is discussed in the case of Calladine-Smith v Saveorder Ltd, as to whether the "contrary" means the contrary of the allegation that the letter was properly addressed, prepaid and posted, or whether it refers to the contrary of the deeming provision that the letter in question was delivered in the ordinary course of post. In this particular case, a letter was shown to have been properly addressed, pre-paid and posted, but not received. On a balance of probabilities the court accepted that the "contrary" to the deemed provision had been proved, the letter was not received, and therefore the deemed provision could not hold.[15]

Section 8

Section 8 specifies that, in general, a measurement of distance refers to measurement in a straight line on a horizontal plane.[16]

Section 16 – General savings

The following cases are relevant to this section:

  • Hough v Windus (1884) 12 QBD 224, CA
  • R v Fisher (Charles) [1969] 1 WLR 8, CA
  • R v West London Stipendiary Magistrate, ex parte Simeon [1983] AC 234, HL

Section 18 – Duplicated offences

Section 18 provides:

Where an act or omission constitutes an offence under two or more Acts, or both under an Act and at common law, the offender shall, unless the contrary intention appears, be liable to be prosecuted and punished under either or any of those Acts or at common law, but shall not be liable to be punished more than once for the same offence.[17]

This section replaces section 33 of the Interpretation Act 1889.[18] Humphreys J. said that that section did not add anything to the common law, or detract anything from it.[19]

"... shall not be liable to be punished more than once for the same offence"

The words "same offence" at the end of section 18 do not mean "same act" or "same cause". A person may be punished more than once for the same act.[20] Two prosecutions for a single false statement in a brochure is not oppressive.[21]

See also Williams v Hallam (1943) 112 LJKB 353, (1943) 59 TLR 287, (1943) 41 LGR 165.


The word "Act" means Act of Parliament.[22] It includes a local and personal or private Act.[23]

A reference to an Act in this section is a reference to an Act to which this section applies.[11]

This section applies to Acts whenever passed.[24] It applies to Measures of the General Synod of the Church of England, and, so far as it relates to Acts passed before 1 January 1979, to measures of the Church Assembly passed after 28 May 1925, as it applies to Acts.[25] It applies to an Act of the Scottish Parliament as it applies to an "Act".[26]

For the application of this section to subordinate legislation, see section 23. And see also section 23A(2)(b).

Section 19

For section 19(1), see Citation of United Kingdom legislation § Interpretation of citations by year, statute, session, chapter, number or letter.

Section 23A

This section was inserted by section 125 of, and paragraph 16(2) of Schedule 8 to, the Scotland Act 1998.

See also


  • Halsbury's Statutes. Fourth Edition. 2008 Reissue. Volume 41. Page 796.
  • Archbold Criminal Pleading, Evidence and Practice. 1999. Appendix A.
  • Current Law Statutes Annotated 1978
  1. ^ a b The citation of this Act by this short title is authorised by section 27 of this Act.
  2. ^ The Interpretation Act 1978, section 26.
  3. ^ The Interpretation Act 1978, section 22(1)
  4. ^ The Interpretation Act 1978, section 22(3)
  5. ^ The Interpretation Act 1978, section 23(1)
  6. ^ The Interpretation Act 1978, section 23(3)
  7. ^ The Interpretation Act 1978, section 23A
  8. ^ The Interpretation Act 1978, section 23B
  9. ^ The Interpretation Act 1978, section 25 and Schedule 3
  10. ^ The Interpretation Act (Northern Ireland) 1954
  11. ^ a b The Interpretation Act 1978, section 21(2)
  12. ^ The Interpretation Act, section 6
  13. ^ Archbold Criminal Pleading, Evidence and Practice, 1999, para 4-209
  14. ^ "Interpretation Act 1978: Section 7",, The National Archives, 1978 c. 30 (s. 7)
  15. ^ Calladine-Smith v Saveorder Ltd [2011] EWHC 2501 (Ch), [2011] 44 EG 108 (5 July 2011), High Court (England and Wales)
  16. ^ The Interpretation Act, section 8
  17. ^ Copy of section 18 from
  18. ^ Archbold Criminal Pleading, Evidence and Practice, 1999, para 4–123
  19. ^ R v Thomas [1950] 1 KB 26 at 31 to 33, 33 Cr App R 200 at 204, CCA
  20. ^ R v Thomas [1950] 1 KB 26, 33 Cr App R 200, [1949] 2 All ER 662, CCA
  21. ^ R v Thomson Holidays Ltd [1974] QB 592, [1974] 2 WLR 371, [1974] 1 All ER 823, 58 Cr App R 429, CA
  22. ^ The Interpretation Act 1978, sections 5 and 22(1) and Schedule 1 (as amended by the Scotland Act 1998, section 125 and Schedule 8, paragraph 16(3))
  23. ^ The Interpretation Act 1978, section 21(1)
  24. ^ The Interpretation Act 1978, section 22(1) and Schedule 2, Part I, paragraph 1
  25. ^ The Interpretation Act 1978, sections 22(3) and 26
  26. ^ The Interpretation Act 1978, section 23A(2)(a) (as inserted by the Scotland Act 1998, section 125 and Schedule 8, paragraph 16(2))
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Interpretation Act 1978
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