Here’s a good list that we’ve found for how long to keep your records:

2 YEARS
General correspondence
Requisitions

3 YEARS
Personnel files, terminated
Bank reconciliations
Petty cash vouchers
Expired insurance policies

6 YEARS
Monthly trial balances
Employee withholding tax statements
Employee disability benefits records

7 YEARS
Inventory records
Payroll records
Expense reports
Payable and receivable ledgers
Expired contracts and agreements
Purchasing correspondence
Purchase orders
Invoices and other sales records
Plant cost ledgers

8 YEARS
Checks other than those described below
Vouchers for payments to vendors, employees, etc.
Expired deeds, mortgages and easements

INDEFINITELY
Audit reports and financial statements
Annual trial balances
Checks for taxes, capital purchases, important contracts
Capital stocks and bonds
Cash books
Contracts and agreements in force
Copyrights, patents, trademark registrations
Deeds, mortgages and easements in force
Legal and tax correspondence
Tax returns
General ledgers and journals
Bylaws, charter, minute-books
Insurance records:  accidents, claims, etc.
Depreciation schedules
Independent property appraisals