Here is a sample approach
DECLARE @T TABLE
(
srno INT,
billno INT,
particular VARCHAR(100),
Qty INT,
rate INT,
vat INT,
amount INT,
paid INT,
balance INT
)
INSERT INTO @T
SELECT 1,25,'aaa',5,20,5,105,400,135 UNION ALL
SELECT 2,25,'qqq',5,50,5,225,400,135 UNION ALL
SELECT 3,25,'fff',10,20,5,205,400,135 UNION ALL
SELECT 4,26,'aaa',10,20,5,205,300,245 UNION ALL
SELECT 5,26,'fff',10,20,5,205,300,245
SELECT
CASE WHEN T2.srno = T1.srno THEN RowNo ELSE NULL END AS srno,
CASE WHEN T2.srno = T1.srno THEN T1.billno ELSE NULL END AS billno,
particular, Qty, rate, vat, amount,
CASE WHEN T2.srno = T1.srno THEN T1.paid ELSE NULL END paid,
CASE WHEN T2.srno = T1.srno THEN T1.balance ELSE NULL END balance
FROM @T T1
INNER JOIN
(
SELECT ROW_NUMBER() OVER (Order by billNo) AS RowNo, Min(srno) AS srno, billno FROM @T
GROUP BY billno
) T2 ON T1.billno = T2.billno
ORDER BY T1.srNo, BillNo