In case turnover increases as a `one off` and the business does not wish to register for VAT.
We have to write to the HMRC with evidence to convince them that turnover will not go over £83k (current de-registration threshold) in next 12 months.
HMRC Link below (see bottom of the page):
https://www.gov.uk/vat-registration/when-to-register
Primary legislation (see Clause 3):
http://www.legislation.gov.uk/ukpga/1994/23/schedule/1