Hi V8 I work for a firm of chartered surveyors managing large clients business rates liabilities and have an excellent knowledge of the legislation and case law surrounding business rates. You need to ask the billing authority how the small business rate relief was incorrectly awarded at the time the liability was initially raised. You would needed to have applied at the time, only been liable for one hereditament (thats business premises to you and me!) and have an Rateable Value of less then £15k (£21.5k in Greater London). This should not be something they can change their mind about unless they miscalculated the charge at the time. If they miscalculated quote 'ENCON Insulations V Nottingham' which is a legal case regarding whether a rate account was billed 'as soon a praticable'. Generally speaking the error would need to have been rectified 'as soon as praticable', which whilst this time period is not defined is accepted as being in the rate year (1st April to 31 March period) in which the error was made plus a few extar months if it was near the end of the year. I hope this helps if you need any more assistance tell me exactly what the Billing Authority (Council) say and also a clue which one it is and I may be able to come up with something for you. GOOD LUCK AND DONT BACK DOWN