You are selecting DDate three times. You need to use 'as' to name them:
SELECT Customers.*,
CProfit.Pdate, CProfit.Pbalance,
Deposit.Ddate, Deposit.AmountDeposit,
LPB.Ddate as LPBDate, LPB.Balance,
Loan.Ddate as LoanDate, Loan.LoanAmount,
LoanPaid.Ddate, LoanPaid.PaidAmount,
OPB.Ddate as OPBDate,OPB.Balance,
Withdrawal.Ddate, Withdrawal.WithdrawalAmount FROM OPB INNER JOIN
(Deposit INNER JOIN (Loan INNER JOIN (LPB INNER JOIN (LoanPaid INNER JOIN (CProfit INNER JOIN
(Withdrawal INNER JOIN Customers ON
Withdrawal.CID=Customers.CID) ON
CProfit.CID=Customers.CID) ON
LoanPaid.CID=Customers.CID) ON
LPB.CID=Customers.CID) ON
Loan.CID=Customers.CID) ON
Deposit.CID=Customers.CID) ON
OPB.CID=Customers.CID
ORDER BY Customers.CID
For your question:
SELECT max(LPB.Ddate) -- assuming this is the one you want
FROM OPB INNER JOIN
(Deposit INNER JOIN (Loan INNER JOIN (LPB INNER JOIN (LoanPaid INNER JOIN (CProfit INNER JOIN
(Withdrawal INNER JOIN Customers ON
Withdrawal.CID=Customers.CID) ON
CProfit.CID=Customers.CID) ON
LoanPaid.CID=Customers.CID) ON
LPB.CID=Customers.CID) ON
Loan.CID=Customers.CID) ON
Deposit.CID=Customers.CID) ON
OPB.CID=Customers.CID
you could also do this:
select max(LoanDate)
from
(
SELECT Customers.*,
CProfit.Pdate, CProfit.Pbalance,
Deposit.Ddate, Deposit.AmountDeposit,
LPB.Ddate as LPBDate, LPB.Balance,
Loan.Ddate as LoanDate, Loan.LoanAmount,
LoanPaid.Ddate as LoanPaidDate, LoanPaid.PaidAmount,
OPB.Ddate,OPB.Balance,
Withdrawal.Ddate, Withdrawal.WithdrawalAmount FROM OPB INNER JOIN
(Deposit INNER JOIN (Loan INNER JOIN (LPB INNER JOIN (LoanPaid INNER JOIN (CProfit INNER JOIN
(Withdrawal INNER JOIN Customers ON
Withdrawal.CID=Customers.CID) ON
CProfit.CID=Customers.CID) ON
LoanPaid.CID=Customers.CID) ON
LPB.CID=Customers.CID) ON
Loan.CID=Customers.CID) ON
Deposit.CID=Customers.CID) ON
OPB.CID=Customers.CID
ORDER BY Customers.CID
)