As most margarine or non dairy products are fortified with vitamin D, there is a need to read the labels.
Quoted from : http://www.vegfamily.com/dietician/0605a.htm
“Vitamin D2 is plant-derived while vitamin D3 is usually animal derived, so vegans need to read labels to determine the source of the vitamin D they are taking. Some companies do provide D3 from plants, but it does not appear to be common. Some vegans are comfortable taking animal-derived D3, since it is a relatively miniscule contribution to animal suffering. This, of course, is a personal choice.”