England & Wales:

• 4th January 2009 – EPC required for the construction, sale or rent of all commercial buildings
   
• 1st October 2008 – DEC required for all public buildings with floor a area over 1,000sqm

Scotland:

• Now – EPC required on all commercial new builds
   
• 4th January 2009 – DEC required for the construction, sale or rent of all commercial buildings
   
• 4th January 2009 – DEC required on all public buildings

Northern Ireland:

• Early 2008 – EPC required on all commercial new builds
   
• Mid 2008 – Existing buildings which are being sold
   
• Late 2008 onwards – buildings which are being rented and the introduction of DECs in large public sector buildings