UK Income Tax calculation problem

[Nosmas]

Some years ago I designed an Excel spreadsheet to calculate my own (and anybody else's) tax liability. It has always calculated the correct tax due for the year - until now.

I have only recently realised that I had misread the rules introduced from 2008/09 (when the 10% tax rate was abolished) which introduced a 10% rate for Savings income up to £2,320 (£2,440 for 2009/10), and am having trouble in constructing an accurate formula to determine what amount of income is taxable at the 10% Savings Rate.

In my workbook I use named cells in the formulae, and for the purpose of this problem I use 'BSlice' for the bottom slice of income i.e. earned income such as salary, pension etc, 'MSlice' for the middle slice i.e. savings income, 'TSlice' for the top slice i.e. dividends, 'CPA' for claimable Personal Allowance (after adjusting for age enhancement or income restriction), and 'SavLmt' for the maximum income taxable at the 10% Savings Rate.

Using these names can anyone with sufficient knowledge of UK tax please suggest a workable formula such as: -

'=IF(BSlice>=(CPA+SavLmt),0,IF(BSlice>=CPA,SavLmt-(BSlice-CPA),IF(AND(BSlice=0,MSlice-CPA>=SavLmt),SavLmt,MSlice-(CPA-BSlice)))' - which I am afraid does not work for all variables of BSlice and MSlice.

 

[Nosmas]

Bump this to the top of the pile in the hope that someone may view and provide an answer. Thanks.

 

[Nosmas]

Bump again in the hope there is someone out there with knowledge of both UK Income Tax and Excel who may be able to help!!!