The eligibility, entitlement and explanation may vary over the lifetime of a case. The lifetime of a case is the period of time between the case's start and end dates, inclusive. Each case may bear an actual or expected start date; if an actual start date is present then it is used as the start of the case, otherwise the expected start date will be used. Similarly, a case may have an actual end date and/or an expected end date, which governs the end date of the case's lifetime (with the actual date taking precedence over any expected date).
Each product is configured to specify whether or not it allows open-ended cases.
Open-ended cases may give rise to open-ended decisions and, ultimately, open-ended financial schedules (i.e. "pay until further notice").
In practice, each open-ended case will ultimately end due to some real-world event (and an end date will be recorded, and the case will eventually be closed).
The lifetime of a case may include:
These are periods which have already occurred, and (assuming that the agency has a correct record of all pertinent real-world events) will have been correctly calculated and assessed. For financial components, these past periods will have already been paid (or billed). Any retrospective reassessment of past periods (arising from corrections, or a lag between events occurring in the real world and their subsequent notification to the agency) may result in changes to the determination for a past period, and for these periods the system may need to make corrections to financials, e.g. through the use of over/under payment cases.
These are periods which have yet to occur, and represent the system's "best guess" regarding determination according to what is already known about the real world. New events which come to light may cause this "best guess" to change, but in general a change in prediction of future eligibility/entitlement will not require corrections to financials (except, perhaps, if payments are made in advance rather than in arrears).
Because a case's determination is a value calculated for the case's lifetime, any change in the case's start or end date (e.g. the extension of a case's expected end date) will cause the case to be reassessed. From a CER perspective, the case's start and end dates are simply input data in the same way that evidence, personal data and rates are.
In general, the eligibility, entitlement and explanation for a case will tend to change on the same dates. However, in some cases, not all will change - for example, it is possible for a case to remain constantly ineligible, but the reason for why the case is ineligible may vary over time, and hence the case's explanation may change value on a date even though the case's eligibility does not change value on that date.
Of course, the future gradually becomes the past at every passing moment; and so if "left unchecked" (i.e. there are no changes to input data), the predictions made about future eligibility/entitlement will gently flow into past "actual" eligibility/entitlement, and will be used as the basis for new financials.