How to mark information
You need to mark information correctly so that people understand how to protect and share it.
Do
- Write security classifications in all capitals
- Clearly mark OFFICIAL, SECRET and TOP SECRET information
Don’t
- Do not classify information higher than it needs
- Do not use OFFICIAL-SENSITIVE as a security classification
OFFICIAL information
You need to mark information as OFFICIAL when it is practical to do so.
If the information can be printed out, add the marking to the header and footer.
You should also mark information in emails. On Defence devices, you are usually prompted to select a marking.
Use OFFICIAL-SENSITIVE correctly
OFFICIAL-SENSITIVE is not a security classification. It is an additional marking.
Only use OFFICIAL-SENSITIVE if there are sensitive details in OFFICIAL information.
Check how to apply OFFICIAL-SENSITIVE (opens in a new tab).
SECRET and TOP SECRET information
You must clearly mark SECRET and TOP SECRET information.
If the information can be printed out, add the marking to the header and footer.
You must mark information in emails. On Defence devices, you are usually prompted to select a marking.
Add more details
Often, you can add more details to tell people how to handle and protect information.
Add details after the classification marking, like this:
CLASSIFICATION - HANDLING INSTRUCTION - DESCRIPTOR
This includes the additional marking of OFFICIAL-SENSITIVE. For example:
OFFICIAL-SENSITIVE - RECIPIENTS ONLY - COMMERCIAL
Use the official list
The UK Government and MOD use a set of standard markings.
Examples include:
- RECIPIENTS ONLY for information that must be handled by named individuals on a strict need-to-know basis
- LOCSEN for information that staff overseas cannot access
- PERSONAL DATA for information that can identify a living person
You need to check the full list on GOV.UK (opens in a new tab).
Updated August 2023