If you want to claim a deduction but you don’t have a receipt for that transaction, you may be able to use the bank statement. If you paid the expenses electronically, your bank statement will be useful to support the transaction as long as it contains enough details.
If the bank statement shows Telstra, it is reasonablly regarded as telephone and internent costs and it can be a substantiation. However, if bank statement shows Woolworths, no one knows what were purchased, maybe milk, maybe stationary. In this case, the bank statement cannot be a substantiation.
However, you can claim up to $300 without receipts/invoices as long as you actually spent.