All Self Assessment returns for 2012/13 need to be made online from 1 November, as the paper return deadline closed on Halloween - 31 October - and anyone submitting paper returns late will automatically receive a penalty.
Those who send HMRC a paper tax return from November onwards will receive a £100 late-filing penalty - even if they have no tax to pay, or pay their tax bill on time.
The deadline for online filing of the 2012/13 tax return is 31 January 2014.
To file online, taxpayers must register with HMRC, click HERE. Registrants will receive an activation code by post.
HMRC is advising those who need to register and file their tax return online to allow sufficient time for this process.