The Law Society’s Gazette, 17 April 1991 at p. 16, included the following guidance notes when the rate of VAT increased from 15% to 17.5% on 1 April 1991. These notes should be relevant for future rate changes:
Civil and criminal bills for assessment by area offices: VAT rate rise
Drawing bills for assessment
Where the entirety of the work was undertaken and disbursements paid, either (a) before 1 April, or (b) after that date, solicitors may continue to draw bills and complete relevant claim forms as at present. The only difference is that in the former case VAT is applied at 15%, whereas in the latter the new rate of 17.5% applies.