Have a look at example:
DECLARE @tmp TABLE(ID INT IDENTITY(1,1), PaymentIn INT, PaymentOut INT)
INSERT INTO @tmp (PaymentIn, PaymentOut)
VALUES(50000, 0), (0, 2000),
(0, 3000), (0, 2500),
(0, 2500), (0, 3000),
(0, 3000), (0, 2000),
(0, 1000), (0, 2000)
SELECT t1.ID, t1.PaymentIn, t1.PaymentOut, (SELECT SUM(t2.Balance)
FROM
(
SELECT ID, PaymentIn, PaymentOut, PaymentIn AS Balance
FROM @tmp
UNION ALL
SELECT ID, PaymentIn, PaymentOut, PaymentOut *-1 AS Balance
FROM @tmp
) AS t2 WHERE t2.ID<=t1.ID) AS Total
FROM @tmp AS t1
Result:
ID Pa.In Pa.Out Total
1 50000 0 50000
2 0 2000 48000
3 0 3000 45000
4 0 2500 42500
5 0 2500 40000
6 0 3000 37000
7 0 3000 34000
8 0 2000 32000
9 0 1000 31000
10 0 2000 29000