Most schedules of loss are divided into past loss (loss that has already been suffered) and future loss (loss that will occur in the future). With past loss the tribunal is trying to decide what has already happened, while with future loss they are predicting what will happen.
This distinction makes more sense in a example. If you are dismissed, you lose the salary you were being paid. Assuming that you have a tribunal hearing six months after your dismissal, and you are still unemployed, you have a past loss of six months earnings. That is money you would have been paid had you not been dismissed. Unless you have lined up a job starting the day after the tribunal hearing, you also have future loss — money that you wouldn’t have been paid yet, but would be expecting had you not been dismissed. So the tribunal needs to decide what that loss will be, by predicting when you will get a new job.
Normally, you will prepare your schedule of loss well before the hearing. But you should normally claim past loss up to the hearing (unless you know the loss will stop before that point, for example, if you’ve secured an equally well paying job). This is because the schedule will be used by the tribunal at the hearing. So it needs to reflect the position they will be in.
Otherwise, you get into a situation in which the tribunal is looking at a schedule thinking ‘I need to think about the past loss that is on this schedule as past loss. Then I need to think about the part of the future loss on this schedule that is actually now past loss. And then I need to think about the actual future loss.’ This is just too confusing.
This means that circumstances may change before the hearing, making the schedule inaccurate. For example, you may find a new job. If this happens, just update the schedule to reflect the new situation.