Below dynamic query will set StartDate and EndDate to 1st of March to 30th April as UK financial year.
DECLARE @StartDate DATETIME
DECLARE @EndDate DATETIME
SET @StartDate = DATEADD(dd,0, DATEDIFF(dd,0, DATEADD( mm, -(((12 + DATEPART(m, getDate())) - 4)%12), getDate() ) - datePart(d,DATEADD( mm, -(((12 + DATEPART(m, getDate())) - 4)%12),getDate() ))+1 ) )
SET @EndDate = DATEADD(SS,-1,DATEADD(mm,12,@StartDate))
SELECT @StartDate,@EndDate
Note: to get different dates you can play around StartDate query to get different dates based on your requirements.