Wild Carrot is a common white Umbellifer (ie with white umbrella shaped flower heads) in grassy places, especially on lime, but rarer further north.

There are certain features that are helpful in identification ...
(a) the fringes attached to the flower heads
(b) the centre flower of the umbels often being red
(c) after flowering, the flower head gradually folds inwards to become like a miniature bird's nest and then almost a ball

In flower from mid to late summer.