Thank you for pointing out proper posting etiquette. I had not seen that article before and I apologize.

IF OBJECT_ID('TempDB..#InterestRates','U') IS NOT NULL

DROP TABLE #InterestRates

CREATE TABLE #InterestRates

(

[InterestRate] [float] NULL,

[Month] [int] NULL,

[year] [int] NULL

)

INSERT INTO #InterestRates

(InterestRate,[Month],[Year])

SELECT '0.105','8','2007' UNION ALL

SELECT '0.105','9','2007' UNION ALL

SELECT '0.105','10','2007' UNION ALL

SELECT '0.105','11','2007' UNION ALL

SELECT '0.105','12','2007' UNION ALL

SELECT '0.105','1','2008' UNION ALL

SELECT '0.105','2','2008' UNION ALL

SELECT '0.105','3','2008' UNION ALL

SELECT '0.105','4','2008' UNION ALL

SELECT '0.105','5','2008' UNION ALL

SELECT '0.105','6','2008' UNION ALL

SELECT '0.105','7','2008' UNION ALL

SELECT '0.105','8','2008' UNION ALL

SELECT '0.105','9','2008' UNION ALL

SELECT '0.105','10','2008' UNION ALL

SELECT '0.105','11','2008' UNION ALL

SELECT '0.105','12','2008' UNION ALL

SELECT '0.105','1','2009' UNION ALL

SELECT '0.105','2','2009' UNION ALL

SELECT '0.105','3','2009' UNION ALL

SELECT '0.105','4','2009' UNION ALL

SELECT '0.105','5','2009' UNION ALL

SELECT '0.105','6','2009' UNION ALL

SELECT '0.0067','7','2009' UNION ALL

SELECT '0.0067','8','2009' UNION ALL

SELECT '0.0067','9','2009' UNION ALL

SELECT '0.0055','10','2009' UNION ALL

SELECT '0.0055','11','2009' UNION ALL

SELECT '0.0055','12','2009' UNION ALL

SELECT '0.0055','1','2010' UNION ALL

SELECT '0.0055','2','2010'

IF OBJECT_ID('TempDB..#Refunds','U') IS NOT NULL

DROP TABLE #Refunds

CREATE TABLE #Refunds

(

[Acct_no] [varchar(20)] NULL,

[Amount] [float] NULL,

[Month] [int] NULL,

[year] [int] NULL

)

INSERT INTO #Refunds

(Acct_no,Amount, [Month],[year])

SELECT '1271003600','333.107456586203','1','2008' UNION ALL

SELECT '1271003600','87.6816131178288','1','2009' UNION ALL

SELECT '1271003600','103.602002310821','2','2008' UNION ALL

SELECT '1271003600','81.9722910242125','2','2009' UNION ALL

SELECT '1271003600','72.3401647559977','3','2008' UNION ALL

SELECT '1271003600','86.1625895742832','3','2009' UNION ALL

SELECT '1271003600','103.361218989159','4','2008' UNION ALL

SELECT '1271003600','84.6065155612006','4','2009' UNION ALL

SELECT '1271003600','92.2834655375568','5','2008' UNION ALL

SELECT '1271003600','84.6688365382596','5','2009' UNION ALL

SELECT '1271003600','89.0687598341003','6','2008' UNION ALL

SELECT '1271003600','79.1241550533365','6','2009' UNION ALL

SELECT '1271003600','123.131877952709','7','2008' UNION ALL

SELECT '1271003600','89.3938505146093','7','2009' UNION ALL

SELECT '1271003600','87.2510378856992','8','2007' UNION ALL

SELECT '1271003600','94.0687846832911','8','2008' UNION ALL

SELECT '1271003600','340.381691069552','8','2009' UNION ALL

SELECT '1271003600','80.3632310400272','9','2007' UNION ALL

SELECT '1271003600','121.96840107118','9','2008' UNION ALL

SELECT '1271003600','87.1037670414245','10','2007' UNION ALL

SELECT '1271003600','94.9861134399298','10','2008' UNION ALL

SELECT '1271003600','73.8008470324637','11','2007' UNION ALL

SELECT '1271003600','78.537373182859','11','2008' UNION ALL

SELECT '1271003600','90.7988754111144','12','2007' UNION ALL

SELECT '1271003600','88.4954811818565','12','2008' UNION ALL

SELECT '1271005700 ','651.764','1','2008' UNION ALL

SELECT '1271005700 ','650.766','1','2009' UNION ALL

SELECT '1271005700 ','897.994','2','2008' UNION ALL

SELECT '1271005700 ','688.486','2','2009' UNION ALL

SELECT '1271005700 ','721.466','3','2008' UNION ALL

SELECT '1271005700 ','718.654','3','2009' UNION ALL

SELECT '1271005700 ','913.072','4','2008' UNION ALL

SELECT '1271005700 ','863.224','4','2009' UNION ALL

SELECT '1271005700 ','735.081','5','2008' UNION ALL

SELECT '1271005700 ','647.368','5','2009' UNION ALL

SELECT '1271005700 ','607.721','6','2008' UNION ALL

SELECT '1271005700 ','580.359','6','2009' UNION ALL

SELECT '1271005700 ','718.969','7','2008' UNION ALL

SELECT '1271005700 ','693.378','7','2009' UNION ALL

SELECT '1271005700 ','734.005','8','2007' UNION ALL

SELECT '1271005700 ','591.788','8','2008' UNION ALL

SELECT '1271005700 ','679.773','8','2009' UNION ALL

SELECT '1271005700 ','560.296','9','2007' UNION ALL

SELECT '1271005700 ','685.047','9','2008' UNION ALL

SELECT '1271005700 ','682.834','10','2007' UNION ALL

SELECT '1271005700 ','608.706','10','2008' UNION ALL

SELECT '1271005700 ','586.172','11','2007' UNION ALL

SELECT '1271005700 ','650.191','11','2008' UNION ALL

SELECT '1271005700 ','858.672','12','2007' UNION ALL

SELECT '1271005700 ','711.708','12','2008'

The formula I am using to calculate interest is

Interest(month) =( Refund(PreviousMonth) + Interest(Previous Month) ) * (1+ InterestRate(Month)/12)

For Example

Interest(August 2008) = ( 0 + 0)*(1+.105/12) = 0

Interest(September 2008) = ( 87.25 + 0 )*(1+.105/12) = 88.01

Interest(October 2008) = (80.36 + 88.01)*(1+.105/12) = 169.851

There are no more refunds to add after August 2009 but we continue to accrue interest until February 2010

For the account above I get a Final balance of 3011.41

If anything above is unclear please let me know and thank you for your help.