Confidence: It's likely to be this, but I can't be certain.
Notes: Going by the shape of the rear edge of the central band on the forewing it looks better for truncata than citrata. Waring, Townsend and Lewington says the most reliable feature for seperating the species is the presence of a longer and more pointed projection on this line on C.citrata. The projection doesn't appear to be long enough on this moth for citrata. The flight time wouldn't necessarily rule out C. citrata but is more likely to suggest C. truncata.