The books of account of every company relating to a period of __________________ immediately preceding a financial year together with the vouchers relevant to any entry in such books of account shall be kept in good order. 

 Explanation: Section 128. Books of account, etc., to be kept by company- (5) The books of account of every company relating to a period of not less than eight financial years immediately preceding a financial year, or where the company had been in existence for a period less than eight years, in respect of all the preceding years together with the vouchers relevant to any entry in such books of account shall be kept in good order: Provided that where an investigation has been ordered in respect of the company under Chapter XIV, the Central Government may direct that the books of account may be kept for such longer period as it may deem fit.