In the run up to the self assessment deadline on 31 January 2007, HM Revenue and Customs (HMRC) ran a telephone campaign to help self assessment customers comply with their statutory obligations and avoid penalties and interest charges.853,158 customers were selected to receive an enabling telephone call to remind them that 31 January 2007 was the deadline for returning their 2005-06 self assessment tax return and paying any money due.These calls were made throughout the week, including the weekend (between 11:30 and 16:30) when some customers are more likely to be available.Up to 200 staff have been involved in handling these calls at a cost of £350,000.Data extracts taken from the self assessment computer system just before the campaign started and some further data extracts taken during the campaign, were used to identify the customers to be telephoned.Approximately 10 per cent. of customers contacted indicated that they had already submitted their returns during this self assessment telephony reminder campaign.