Here's the results of the updated code:

Contract    Serial      Period      Period    PeriodEnd   StartDate   CallOff   Day
Number      Number      Group     ...

Take a look at this to start:SET NOCOUNT ON;

CREATE TABLE #Data (
    SerialNumber varchar(25) NOT NULL,
    ContractNumber varchar(10) NOT NULL,
    StartDate date NOT NULL,
    CallOffDate date NOT NULL

Here's that scenario in the test data: SET NOCOUNT ON;

CREATE TABLE #tempTvol (
  [Site] int,
  Seq int,
  Concur char(1),
  [Value] float
);
INSERT INTO...

Try this: SET NOCOUNT ON;

CREATE TABLE #tempTvol (
    [Site] int,
    Seq int,
    Concur char(1),
    [Value] float
);
INSERT INTO #tempTvol
    VALUES     (1, 1, NULL, 1.8)
            ,(1, 2, 'T',...