TSQL issue when updating value and outputing inserted value into log table - sql-server

Question

I update a ClientFunds.Balance table column with a value and use the Ouput Inserted.Balance clause to write the value to a log table.
Occasionally the value written to the ClientFunds table is truncated whilst the value written to the log table is always correct.
First, I fill this table with the details of what will be updated on the ClientFunds table:
declare #ToUpdate table
(
Id int identity(1,1),
ClientFundId int,
Total decimal (18, 2),
Rate decimal (10, 5)
);
This table will hold the data to be written to the log table:
declare #Updated as table
(
ClientFundId int,
AmountBefore decimal (18,2),
AmountAfter decimal (18,2),
ToUpdateId int
);
Here's how I update the ClientFunds table, using the #ToUpdate table and ouput the log information to the #Updated table. I've snipped a few details of the loop here but you should get the idea:
WHILE ##FETCH_STATUS = 0
BEGIN
update cf
set cf.Balance = cf.Balance - (up.Total * up.Rate)
OUTPUT INSERTED.Id, DELETED.Balance, INSERTED.Balance, up.Id
INTO #Updated
from #ToUpdate up
join dbo.ClientFunds cf on cf.Id = up.ClientFundId
where up.Id = #CurrentId
FETCH NEXT FROM ToUpdate_Cursor into #CurrentId;
END
Now, as I said, occasionally the dbo.ClientFunds.Balance value, which is decimal (18, 2), will be written to the db with the decimal part truncated yet the inserted value output to #ToUpdate retains the correct value.
For instance, one example is 14454.36 being written to the #Updated table, and ultimately the log file, but 14454.00 being written to dbo.ClientFunds.Balance.
Any idea of what could be happening?
Thanks,
Jules