Gastrointestinal endoscopy:

Waiting time is calculated as the total number of days from the date a patient is placed on the waiting list to either the date of removal or the census date, minus any days the patient was not ready for care, and also minus any days the patient waited with a less urgent clinical urgency category than their category at the removal date or at the census date.

Start and end dates
The start of the waiting time is the date the patient was placed on the waiting list. For gastrointestinal endoscopy patients this is the Gastrointestinal endoscopy service request-placed on waiting list date.
For removed patients, the end of the waiting time is the Service request-removal from waiting list date.
For waiting patients, the end of the waiting time is the Hospital waiting list-census date.

Exception for gastrointestinal endoscopy patients who have a clinical urgency category of 9 Surveillance:
- The start of the waiting time is the Gastrointestinal endoscopy service request-surveillance due date.  
- Where the patient was removed before the Gastrointestinal endoscopy service request-surveillance due date, the waiting time should be recorded as 0 (zero).

Not ready for care periods
The total number of days a patient was not ready for care (NRFC) is made up of one or more NRFC periods (Service request-not ready for care period). The NRFC period is the inclusive number of days from the NRFC start date to the NRFC end date. NRFC periods should not overlap however if this occurs the days are only counted once.

Less urgent periods
A patient's clinical urgency can be re-categorised over the course of their wait. 

If the patient had a period during the wait where their clinical urgency category was less urgent than the category at the Service request-removal from waiting list date (for removed patients) or at the Hospital waiting list-census date (for waiting patients), then this period should be subtracted from the total number of days waited. If a day within a less urgent period has already been excluded due to a Service request-not ready for care period, the day is excluded only once.

When a patient is removed from a waiting list and requires reinstatement, the same waiting list entry should be reinstated where possible in order to continue the patient's waiting time from that previously accrued, with a not ready for care period applied where appropriate.

Note: When calculating less urgent periods for gastrointestinal endoscopy patients, clinical urgency category 9 (Surveillance) is excluded. The less urgent period is only applied to movement between categories 4 (Urgent), 5 (Semi-urgent) and 6 (Non-urgent).

Specialist outpatient:

The waiting time is calculated as the total number of days from the Referral received date (data element 16) to the Removal datetime (data element 25) or Census date, minus any days the specialist outpatient clinic referral required further information, the patient was waiting with a less urgent clinical category than the clinical urgency category at the Removal date (for Part A) or at the Census date (for Part B), and any days the patient was not ready for care. 

Uncategorised periods 
There may be a period of time between when the specialist outpatient clinic referral is received and a clinician is able to assess the referral. This is referred to as an uncategorised period. An uncategorised period is counted in the patient's waiting time. 

Awaiting information periods 
If after reviewing the referral, insufficient information is available in the referral to accept and categorise the specialist outpatient clinic request, there may be a period where the clinic is awaiting information. An awaiting information period is not counted towards the patient's waiting time. 

Not ready for care periods 
The total number of days a patient was NRFC is made up of one or more NRFC periods. The NRFC period is the inclusive number of days from the NRFC start date to the NRFC end date. NRFC periods should not overlap however if this occurs the days are only counted once. 

Less urgent periods 
A patient's clinical urgency category can be recategorised over the course of their wait. If the patient had a period during the wait where the Clinical urgency category (data element 19) was less urgent than the category at the Removal datetime (data element 25) or at the Census date, then this period should be subtracted from the total number of days waited. If a day has already been excluded due to an NRFC period, the day is excluded only once.