I don’t keep all receipts for all of the purchases, is it a problem?

It’s important to keep all the receipts if you are going to report any purchases.

Your records should include bills, receipts, invoices, cash-register tapes and any other original documents that provide information about the purchased item, such as purchase price and tax paid. These may be maintained in an electronic format.

The provided receipts/bills etc. should also show the rate of tax collected on each sale and any use tax you paid, if any.