How a calculation works

How a calculation runs

SILWise works out a fortnightly and annual figure for each participant in a house, in the same order every time.

1. It checks the house has enough participant bedrooms for everyone living there - the bedrooms a house sets aside for participants, not bedrooms kept for staff. A house can never hold more participants than participant bedrooms.
2. For each participant, it works out their Centrelink benchmark caps - a rental cap and a board cap - from their payment profile, the Centrelink payments recorded for them. This is a ceiling to compare against, not a limit SILWise enforces.
3. It works out that participant’s rent: the house’s fortnightly rent, less any provider contribution, split across the house’s participant bedrooms, less any rent subsidy.
4. It works out each board category for that participant - utilities, repairs and maintenance, household supplies, food, and other items - by totalling every cost-centre line that applies to them, after any subsidy on that line.
5. It adds the rent and every category total together, then converts that fortnightly figure into an annual one for budgeting.
6. Saving the result locks in every participant’s fortnightly and annual figures, stamped with the formula version that produced them.

Rules that catch people out

Rent splits across participant bedrooms, not every bedroom in the house. A bedroom kept for staff never enters the split. Example: a house with 5 bedrooms but only 3 set aside for participants, on $1,800.00 rent, bills $1,800 / 3 = $600.00 per participant, not / 5.

A subsidy is a discount the provider chooses to give, on rent or on one cost-centre line. It only reduces what that participant is charged, not what the house actually spends. Example: a $600.00 rent share with a 20% subsidy bills $480.00.

Each participant has their own Centrelink rental and board cap, from their own payment profile and the rates on the Centrelink rate table. The board cap is half their Disability Support Pension plus their Energy Supplement. Example: on a $1,150.00 pension and a $15.00 supplement, the board cap is $590.00.

A provider contribution reduces rent before it is split, and is not capped at the rent amount. SILWise records this as Provider contribution on the saved calculation. Example: $2,000.00 rent with a $2,000.00 contribution leaves nothing to split - each participant’s rent share is $0.00.

A weekly cost doubles to reach a fortnight; a 90-day shared cost is divided by 90, multiplied by 14, then split across everyone living in the house. Example: a $900.00 90-day electricity bill shared by 3 participants bills $900 / 90 x 14 / 3 = $46.67 each.

Every line is rounded to the cent before it is added up, so the totals on screen always add up exactly. Example: a raw share of $32.005 rounds up to $32.01, never down.

Worked example: Wattle Grove

Wattle Grove has 3 participant bedrooms, $1,650.00 rent a fortnight, no provider contribution, and three participants in residence: Maria, Deng and Priya.

Rent: $1,650 / 3 participant bedrooms = $550.00 each. No rent subsidy applies, so this is the final figure, shown on screen as Rent / FN (FN meaning fortnight).

Utilities: an electricity line ($945.00 per 90 days) and a water line ($270.00 per 90 days), shared three ways: $945 / 90 x 14 / 3 = $49.00, plus $270 / 90 x 14 / 3 = $14.00, totalling $63.00 for everyone.

Repairs and maintenance: a $351.00 repairs line and a $126.00 gardening line, both per 90 days, come to $18.20 plus $6.53 - $24.73 for everyone.

Household supplies: a $94.50 line per 90 days, shared three ways, is $4.90 - only for participants with consumables switched on. Maria and Deng have it on; Priya does not, so hers is $0.00.

Food: breakfast is $18.00 a week, lunch $22.00, and dinner $35.00, each doubled for a fortnight. Maria has all three meals: $150.00. Deng skips breakfast: $114.00. Priya skips dinner: $80.00.

Other items: a $25.00-a-week recreation line, included for everyone, doubles to $50.00 each.

Add rent and every category together for the Total / FN, then multiply by 26.0857 and round to the nearest dollar for the Annualised figure:

Participant	Total / FN	Annualised
Maria	$842.63	$21,981
Deng	$806.63	$21,042
Priya	$767.73	$20,027

Maria’s total: $550.00 rent + $63.00 utilities + $24.73 repairs and maintenance + $4.90 household supplies + $150.00 food + $50.00 other items = $842.63. Annualised: $842.63 x 26.0857 = $21,980.59, which rounds up to $21,981.

Why the formula version matters

Every time you save a calculation, SILWise creates a scenario - a record of that calculation as it stood - stamped with the formula version that produced it. The formula version tracks SILWise’s rent and board formulas, not your house or participant data, and goes up whenever a formula changes.

A scenario saved last month keeps the formula version, and the figures, it had on the day you saved it, even after formulas change. That is what makes a saved calculation reliable evidence: reopening it never produces a different number. To get today’s figures under today’s formulas, follow Run a calculation and save a fresh scenario.