> For the complete documentation index, see [llms.txt](https://help.boomerang3.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.boomerang3.com/boomerang-3-domain-administrator-manual/common_elements/sign.md).
# Sign
Every change of the system state must be confirmed with a user signature. A change can be e.g., a user email change, measuring point calibration adjustment or alarm acceptance.
History of all the changes is stored in database for further reference.
When signing is needed, a “User Signature” form is opened.
If PIN is enabled in the system group and for the user then the sign form looks as below:
To sign:
1. Enter your username and password or PIN.
2. It is good practice to enter a comment that explains the reason for a change. It is possible to make a comment mandatory for a System Group as described in [System Group Settings](/boomerang-3-domain-administrator-manual/admin/settings/settings__system_group_settings.md).
3. Click “Sign” button.
4. The system shall confirm the change has been done.
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