The standard rate of VAT increased from 17.5 per cent to 20 per cent on 4 January 2011.
For any sales of standard-rated goods or services that you make on or after 4 January 2011 you must charge VAT at the 20 per cent rate. If you have a cash business and calculate your VAT using the VAT fraction you must use the VAT fraction of 1/6 on your standard-rated VAT inclusive sales from 4 January 2011.
The change only applies to the standard VAT rate. There are no changes to sales that are zero-rated or reduced-rated for VAT. Similarly, there are no changes to the VAT exemptions. Any sales you make at these rates are unaffected by this change.
More information can be found on the HMRC website here