Supported independent living is rostered in ratios. A 1:3 shift means one worker supporting three residents at once, and — this is the part that makes SIL billing hard — each resident's plan funds a share of that worker's time. One roster entry, three funding sources.
Getting the share right matters in both directions. Bill a plan too much and you are claiming for support a participant did not receive. Bill it too little and you are giving away funded revenue. Both errors are invisible until someone reconciles.
The split follows the ratio, not the house
The naive approach divides the shift cost by the number of residents in the house. The correct approach divides each segment of the shift by the ratio that actually applied during it, because ratios move over a day.
One resident leaves for a day program mid-morning: the 1:3 becomes a 1:2, and from that point the remaining two plans fund the worker between them. Another returns for the evening: the ratio shifts again. Each change creates a segment boundary, and the split is calculated per segment.
Where hand-splitting breaks down
Providers doing this in spreadsheets hit the same failures repeatedly:
- Rounding drift — thirds do not divide evenly, and unrecorded rounding accumulates over a fortnight
- Mid-shift ratio changes averaged away, billing a plan for time the participant was not there
- The roster, the timesheet and the claim each doing their own split, so no two agree
- No record of how a figure was derived when a plan manager queries a line
The rounding has to go somewhere — record where
Split one worker's hour three ways and the cents do not divide cleanly. Somebody's plan carries the extra cent. That is fine — what is not fine is having no record of the decision, because a plan manager reconciling to the cent will find the discrepancy, and you will have no answer.
The standard is simple: the split should reproduce exactly from the roster, and the rounding rule should be written down and applied the same way every time.
What this means for your tooling
The roster is the only place that knows the ratio at every point in time, so the roster is where the split has to be computed. Anything downstream is a re-derivation that can drift.
Nexrosta does ratio splitting at the roster: a 1:3 shift is divided across the residents' plans as you place it, to the cent, with the rounding recorded. Change the ratio mid-shift and the segments recalculate. The claim inherits the roster's split rather than re-deriving it, which is why the two always agree.