A tamper evident bag is a heavy duty bag used to contain high-value products or documents or legally sensitive items, also it is called tamperproof bag, tamper resistant bag, or security bag, security envelopes. 

Cash for deposit in a bank is often placed in a special deposit bag with security features. When used to contain items related to a crime, special evidence bags are used. Authentication of signatures and chain of custody are often required. Tamper evident bags or envelopes are specially designed plastic bags, paper bags, or fabric bags. Bags or envelopes can be made to be tamper resistant to make it difficult for unauthorized entry; often it is more important for these to be tamper evident, to indicate when an unauthorized entry has occurred. Bags and envelopes are often closed by an integral pressure sensitive adhesive on the closing flap; removal of a release liner allows convenient closing of the bag. Several types of security features can be included in the flap structure which are designed to irreversibly indicate opening.

Tamper-indicating security seals employ a variety of mechanisms for operation, each with its own advantages and disadvantages.