All cattle and deer herds are classified with a Tb status, which shows their Tb history.

A herd will be classified as infected (I) if Tb has been confirmed by testing, post-mortem or other approved diagnosis. A newly infected herd will be classified as I1, with a number up to 10 being added for every year it remains infected.
Herds that show no evidence of Tb will be classified as clear (C). A number up to 10 will be added for each year the herd has been confirmed clear of infection after testing.
For a herd to shift from infected to clear, it must have two consecutive clear whole herd tests, with a minimum of six months between tests and no further evidence of disease.

A herd with a clear status will have its status changed to suspended (S) if Tb is suspected but further confirmation is being sought, if it has received stock from an infected herd or of an unknown status, or if testing obligations have not been met.

The herd classification determines the testing regime put in place for that herd, and also affects the movement controls placed on the herd.