As part of HMRC’s powers in the administration and collection of VAT, they are able to issue notices to taxpayers requesting that they give security for payment of any VAT which may become due in the course of providing goods/services, if HMRC believe this necessary for the protection of the revenue. In some instances, this can be a condition of supplying goods/services under a taxable supply and for the repayment of input tax, which can be claimed to the extent it is incurred in the course of making taxable supplies.
Source: thevatpeople.co.uk
