The Average Is Five to Seven Years.
It is important to keep business invoices for tax reasons in case your business gets audited. Business Victoria suggests keeping non-company financial records for five years and keeping "financial records for companies, most employee records and all records of fringe benefits and capital gains" for seven years.
Consider Certain Situations.
If your business has been audited in the past, you should keep all records, regardless of what kind, for seven years. It is smart to have business invoices safely organized and stored for seven years in case they are ever needed as evidence of business purchases, etc.
Depending on the type of business invoice, it is best to keep them for five to seven years. However, if you have been audited before and feel it necessary to keep records for proof, hold all invoices for at least seven years.