How to deal with a bank error

[allanb]

I have a savings account with the Banque Populaire and each year I get the usual computer-generated form telling me how much interest I should enter in which box on the tax return.  It also says that the amount has been reported to the tax office.  This year, i.e. for 2006, the amount on the form cannot possibly be correct (it's impossibly high, so I would be paying too much tax).

My usual conseiller at the bank can't explain it, and arranged a meeting with one of the bank's investment experts.  The investment expert agrees that the number appears to be wrong but he can't explain it either, even after a long phone discussion with one of their systems experts (they have plenty of experts).  They are still working on it, but nobody can do a manual calculation to tell me what the amount should be.  Of course I can write a letter of complaint to the bank, but in the meantime I have to deal with the tax office.

I did my tax declaration on line, using the amount reported by bank, knowing that I would be able to modify the return when I knew the correct number.  But the deadline in my region is 19 June, so I'm running out of time.

It seems to me that I will have to tell the tax office that the bank doesn't know what it's doing, and make my own estimate of the interest.  Has anyone else been in this position?   Is it technically possible to report a number that conflicts with the bank's official form, or is the bank's number locked into your tax file?   If you make a declaration which you know is almost certainly wrong, and pay too much tax as a result, can you make a repayment claim later?

[BJSLIV]

Why not report the amount of interest that was actually credited to your account for the year?

 

[allanb]

Sorry, I should have explained further.  This is a thing called a Compte Moisson (the bank's brand name), and it consists of a fixed-term tax-free savings account called a PEL combined with a term deposit account from which transfers are made into the PEL.  Only the interest on the deposit account is taxable.

As the bank explains it, it's a brilliant invention but it's so complex that they can't undertake to produce statements, so the customer doesn't see the detail of transactions, or the change in the balance, for the full term of the contract. 

I know, I shouldn't have signed up for anything that couldn't be properly explained.  But I had just arrived in France and I was rather busy and I placed my trust in the bank.

None of this would matter if someone in the bank could extract the information from the system when needed: but apparently the bank's own employees don't understand it.