In the 1988 Act, before section 5 insert—
“4A Assured tenancies to be periodic with rent period not exceeding a month

  • (1) Terms of an assured tenancy are of no effect so far as they provide—
    • (a) for a tenancy to be a fixed term tenancy, or
    • (b) for periods of the tenancy to be different from the periods for which rent is payable (“rent periods”).
  • (2) Where terms of an assured tenancy are of no effect by virtue of subsection (1)(a) or (b), the tenancy has effect as a periodic tenancy 15
    under which the periods of the tenancy are the same as the rent periods.
  • (3) Terms of an assured tenancy which provide for the rent periods are of no effect unless each rent period is—
    • (a) a period of 28 days or shorter, or
    • (b) a monthly rent period.
  • (4) Those terms may provide for different rent periods at different times during the assured tenancy (but each rent period must be permitted
    by subsection (3)).
  • (5) Where terms of an assured tenancy are of no effect by virtue of subsection (3), the tenancy has effect as if it provided—
    • (a) for successive rent periods of one month beginning with the first day of the tenancy, and
    • (b) for the rent for each such rent period—
      • (i) to be the amount calculated in accordance with the formula in subsection (6), and
      • (ii) to be due on the first day of the period.
  • (6) The formula is—

    R
    _ × 30 . 42 15
    D

    where—

    R is the rent that would have been due for the first rent period of the tenancy under the terms that are of no effect by virtue of subsection (3);
    D is the number of whole days in that period.

  • (7) Except as provided by subsections (1) and (3), nothing in this section limits any right of the landlord and the tenant to vary a term of a tenancy by agreement.
  • (8) For the purposes of this section, terms of an assured tenancy provide
    for “monthly” rent periods if they provide for rent to be payable for 25
    successive periods of one month, disregarding any provision for the first period to be a different period not exceeding 30 days.”