If one put "2013", one would be using a form of words for the declaration which was non-compliant with what is currently specified by BS7671 ('as amended', whenever).I am aware of that, however I would still suggest that it is incorrect to put the amendment date as 2011 rather than 2013 if it has been designed since then.
Kind Regards, John
Given that Amendment No. 2 (2013) is obviously an Amendment, I would suggest that failure to amend the declarations in it was an oversight. Therefore I would still suggest that it is not correct to state that it is as Amended to 2011.
