Generally, you should hang on to tax records and receipts for three years. But in some cases, longer.  

Always keep receipts, bank statements, invoices, payroll records, and any other documentary evidence that supports an item of income, deduction, or credit shown on your tax return. The best approach to recordkeeping for small businesses is to try to keep as many records as you can. See below a chart from irs.gov that offers some guidance on this.