DECLARE @T TABLE
(
	dataS		date,
	dataPo		date,
	exp		VARCHAR(10),
	nomDoc		VARCHAR(10),
	summaZakrit	money
)
INSERT INTO @T
(
	dataS		,
	dataPo 		,
	exp 		,
	nomDoc 		,
	summaZakrit 
)
VALUES
('01 jan 2018', '31 mar 2018',  'ВГ001', '584 ', 3000.00 ),
('01 mar 2018', '30 apr 2018',  'НР002', '586 ', 5000.00 ),
('01 feb 2018', '28 feb 2018',  'ПДР01', '587 ', 10000.00),
('15 jan 2018', '15 feb 2018',  'ВГ001', '588 ', 2000.00 )

; WITH mm(a) AS
 (
	SELECT number FROM master..spt_values WHERE type = 'p'
 ), grp AS 
 (
	SELECT 	
		OriginFrom = dataS,
		OriginInto = dataPo,
		[dataS] = 
				CASE 
					WHEN b.a = 0 
					THEN dataS 
					ELSE CAST(DATEADD(month, DATEDIFF(month, 0, DATEADD(month,b.a,dataS)), 0) as date)
				END,
		[dataPo] = 
				CASE 
					WHEN EOMONTH(DATEADD(month,b.a,dataS)) > dataPo
					THEN dataPo
					ELSE EOMONTH(DATEADD(month,b.a,dataS))
				END,
		exp	,
		nomDoc 	,	
		summaZakrit
	
		--
	FROM 
		@T	AS A
	INNER JOIN
		mm	AS b
	ON	b.a	<= MONTH(dataPo) - MONTH(datas) 
	WHERE
		a.dataS	<= '31 mar 2018' 
	AND	a.dataPo	>= '01 jan 2018'
)
SELECT 
	dataS		,
	dataPo 		,
	exp 		,
	nomDoc 		,
	summaZakrit	,
	CAST(ROUND(1.* SUMMAZakrit * (1 + DATEDIFF(day,dataS,DataPo)) /(1 + DATEDIFF(day,OriginFrom,OriginInto)),2) as money)
FROM grp