If you use the flat rate scheme for small businesses you should check-out the new flat rates that will apply when the standard rate of VAT increases to 20% on 4 January 2011.

From that date you could be worse off than operating outside the flat rate scheme, it depends on the flat rate that applies to your business sector. If you want to stop using the flat rate scheme you need to inform the VAT office in writing. It’s easiest if you leave the scheme from the start of your next VAT quarter. Once you leave the flat rate scheme you can’t rejoin for at least 12 months.

New flat rates from 4 January 2011

http://www.hmrc.gov.uk/vat/start/schemes/flat-rate.htm#5a