As readers will know the deadline for submitting self assessment returns on-line for the 2008/2009 tax year is 31 January 2010. The deadline for paper returns was 31 October 2009. 31 January 2010 is also the deadline for paying any amount due for 2008/2009. This payment deadline applies for both paper and online filers.
HMRC have issued guidance for tax agents and advisers to help manage the 31 January Self Assessment deadline. The guidance deals with matters such as agent authorisation, security issues, and service issues and is available here