Oh, inherited mess... my favorite! Here's a quick example of using a window function.

SELECT pmts.ID

, pmts.Amount

, pmts.[Status]

, SUM([Amount]) OVER (ORDER BY ID

ROWS BETWEEN UNBOUNDED PRECEDING

AND CURRENT ROW) AS RunAmt

FROM

(SELECT 1 AS ID

, 15 AS Amount

, 'Paid' As [Status]

UNION ALL

SELECT 2, 3, 'Paid'

UNION ALL SELECT 3,10,'Awaiting'

UNION ALL

SELECT 4, 12,'Awaiting') pmts;

If you wanted to do a GROUP BY in your running total, it would be like this (note the PARTITION BY):

SELECT pmts.OwnerID

, pmts.ID

, pmts.Amount

, pmts.[Status]

, SUM([Amount]) OVER (PARTITION BY OwnerID ORDER BY ID

ROWS BETWEEN UNBOUNDED PRECEDING

AND CURRENT ROW) AS RunAmt

FROM

(SELECT 'a' AS OwnerID

, 1 AS ID

, 15 AS Amount

, 'Paid' As [Status]

UNION ALL

SELECT 'a',2, 3, 'Paid'

UNION ALL SELECT 'a',3,10,'Awaiting'

UNION ALL

SELECT 'b',4, 12,'Awaiting') pmts;