The length of time you should keep a cash receipt typically depends on the item or items on the receipt and the purpose of that receipt. Receipts for minor purchases that you do not intend to use for tax deductions, for example, should typically be kept until you are sure you will not return the items on the receipt. If you have receipts for major purchases, however, then you may want to keep those longer, especially if the items are under warranty. When you have a cash receipt with items you are going to use or have used for a tax deduction, then you should typically keep those for up to six or seven years.
A cash receipt is typically a receipt for an item or items that have been paid for using cash, rather than a check or credit card. The amount of time you should keep this kind of receipt often depends on the items on the receipt and the reasons you may have for wanting to keep it. If you have only minor purchases on the receipt, such as items under $100 US Dollars (USD), then you should typically only keep the receipt until the expiration of a return period for those items or until you have used the items up. A cash receipt for groceries, for example, should only be kept until you have used the grocery items.
If you have a cash receipt with larger purchases on it, such as a receipt for electronics equipment that cost more than $100 USD, then you might keep it for the length of the warranty on that item. This allows you to prove that you purchased the item or items, though this is not always necessary for warranties on all items. You can also use the cash receipt as a proof of purchase if you need to return the product within the returns window of the company from which you purchased it.
A cash receipt with one or more items that you are using as a deduction for your taxes should typically be kept longer than the warranty period. Under most situations in the US, you can be audited by the Internet Revenue Service (IRS) up to three years after you file your taxes, though some situations may allow an audit within six years. This means you should keep a cash receipt for any items you claim as a tax deduction for up to six or seven years, in case of an audit.