02/10/2015
5 October 2015 is the deadline for notifying HMRC if you started a new business during 2014-15 (6 April 2014 - 5 April 2015).
What will happen if you forget?
There will be the tax/NIC to pay, which may have grown to a substantial amount if there is more than one year involved, plus interest, and a penalty may also be charged which can be as much as 100% of the 'tax/NIC due' in the most serious cases.
Take a look at this leaflet if you need more information
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/367527/cc-fs11.pdf