A canceled check is a check that has been successfully deposited or cashed, fully processed by the bank, and cleared, meaning the funds have moved from the payer's account to the payee's account. The bank marks it canceled to prevent it from being presented for payment a second time. A canceled check is legal proof of payment. Under the Check Clearing for the 21st Century Act, signed into law on October 28, 2003 and effective October 28, 2004, banks are permitted to process checks electronically and destroy the originals, replacing physical returns with digital images.
Think of a canceled check like a used airline boarding pass: it proves you made the trip, but the airline has already scanned it and it cannot get you on another flight.
Before the Check 21 Act, banks routinely mailed original canceled checks back with your monthly statement. Today, banks capture digital images of the front and back at the time of deposit. Most paper originals are then destroyed according to the bank's retention policies. Banks and credit unions are generally required to keep copies accessible for up to seven years, and most provide free digital access through online or mobile banking.
If you need a copy for an IRS audit, a payment dispute, or a landlord verification and it is not available online, you can request a substitute check from your bank. A substitute check is a legally valid paper reproduction of the front and back images that the IRS accepts as proof of payment. Banks may charge a fee for providing substitute checks for older transactions.
A canceled check has been processed and paid. A voided check is one you intentionally invalidated before it was ever deposited, by writing "VOID" across the front in large letters. You use voided checks when setting up direct deposit or automatic bill payment, providing your routing and account numbers without authorizing an actual payment.
A returned check, commonly called a bounced check, is one the bank refused to honor due to insufficient funds, a closed account, or a signature mismatch. A returned check has not been paid. A stop payment order is a request you make to your bank before a check clears to block it from being processed. None of these is the same as cancellation, which is the normal successful completion of a check transaction.
Sources:
https://www.sofi.com/learn/content/what-is-a-canceled-check/
https://www.pnc.com/insights/personal-finance/spend/what-is-a-canceled-check.html
https://www.citi.com/banking/personal-banking-guide/basic-finance/what-is-a-canceled-check
https://www.thetaxadviser.com/issues/2012/jul/tpp-july-story-02/