You can claim if a patient needs more work during an open CoT under some circumstances.
If the patient goes to the practice the open CoT is with, any additional treatment is considered as part of the existing CoT.
The only exception to this is detailed in DH factsheet 7b Gateway Reference 6990 which states 'The patient is already undergoing a course of treatment and presents with a problem that requires urgent treatment. In these circumstances, the additional treatment should normally be provided as part of the existing course of treatment, as a variation of the treatment plan. In exceptional cases, for example a patient suffers intra-oral trauma as a result of an accident, an urgent course of treatment may be claimed.'
The situation is different if the patient sees a clinician working under a different contract. The clinician must claim for an urgent CoT, charge the patient as normal if appropriate and they'll receive the appropriate UDA.
When submitting a claim for urgent treatment, it cannot be claimed under the continuation rule.