10. Income Tax Expense

The income tax expense comprises:
Current tax expense690632
Adjustment in the current year in relation to prior years(105)(175)
The deferred tax (credit)/expense comprises:
Origination and reversal of temporary differences22(70)(18)
Adjustment in the current year in relation to prior years22206
Total tax expense for the year535445
The total tax charge can be reconciled to the accounting profit as follows:
Total comprehensive income for the year2,1371,885
Total tax expense535445
Profit before tax2,6722,330
Income tax calculated at 22.5% (2013  23.75%)601553
Effect of expenses not deductible5548
Effect of share-based deductions(13)20
Change in UK tax rate(23)(7)
Effect of adjustments in respect of prior years(85)(169)

The tax credit of £35,000 (2013: £90,000) shown within "exceptional and other items" on the face of the statement of comprehensive income, which forms part of the overall tax charge of £535,000 (2013: £445,000) relates to the items analysed in note 4.

The prior year current tax credits in respect of both 2014 and 2013 primarily relate to research and development tax credits.

Reductions in the UK corporation tax rate to 21% (effective from 1st April 2014) and 20% (effective from 1st April 2015) were substantively enacted on 2nd July 2013. Deferred tax balances have been calculated at an effective rate of 20%, being the substantively enacted rate at 30th June 2014. The future rate reductions will affect the Group’s future current tax charges.