HMRC’s internal guidance to staff in respect of distraint is set out in the Debt Management and Banking Manual which is available on HMRC’s website at:
http://www.hmrc.gov.uk/manuals/dmbmanual/DMBM655010.htm
HMRC also publish information about distraint aimed specifically at HMRC customers, including a fact sheet: “Distraint—what it means for you”.
This customer facing guidance is available at:
http://www.hmrc.gov.uk/payinghmrc/problems/dontpav/debts.htm