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Cut the bill period at the day the home stops being shared; divide only the shared stretch. In the first example below, a 30-day period has 11 shared days and 19 lived alone: of $1,650.00 in bills, $605.00 is shared and $1,045.00 belongs in full to the person who stayed. On a 60/40 share that is $1,408.00 for Person A and $242.00 for Person B. Applying 60/40 to the whole month instead would charge Person B $418.00 for days they no longer lived there. Every amount on this page is an example value set by this page.
When two people stop sharing a home in the middle of a billing period, the bills do not stop being shared on the day the address changes. Split the period at that day: the stretch while both still lived there is a shared part, and the stretch after it belongs to whoever stayed. Divide only the shared part by the share you already used; the rest is one person's bill in full. That is the whole method.
Dividing the whole month by the old shares is the common mistake. It charges the person who left for days they were not there, and it charges the person who stayed for only a fraction of the days they lived there alone. The examples below cut one bill period into two parts, show what each person owes, and add every figure back to the original bill total so the arithmetic can be checked end to end.
Take a 30-day period, Day 1 through Day 30. Two people share the home through Day 11; one of them moves out at the start of Day 12, and the other stays. That gives 11 shared days and 19 days lived alone. Three bills cover the whole period.
| Bill | Full period | Shared part | Own part |
|---|---|---|---|
| Rent | $1,500.00 | $550.00 | $950.00 |
| Electric | $90.00 | $33.00 | $57.00 |
| Internet | $60.00 | $22.00 | $38.00 |
| Total | $1,650.00 | $605.00 | $1,045.00 |
Each part is the bill split by days: 11 of 30 days for the shared stretch, 19 of 30 for the stretch lived alone. Rent: $1,500.00 × 11 ÷ 30 = $550.00 and $1,500.00 × 19 ÷ 30 = $950.00. The same cut gives $33.00 / $57.00 for electric and $22.00 / $38.00 for internet. Every row adds back to its full-period bill, and the two part columns add to $1,650.00. These are example values set by this page.
| Person | Shared 60/40 | Own part | Owes |
|---|---|---|---|
| Person A (stays) | $363.00 | $1,045.00 | $1,408.00 |
| Person B (leaves) | $242.00 | $0.00 | $242.00 |
| Total | $605.00 | $1,045.00 | $1,650.00 |
The shared $605.00 is the only amount divided between people, on a 60/40 share set by this page: $605.00 × 60% = $363.00 and $605.00 × 40% = $242.00. The $1,045.00 own part is not divided at all - it goes in full to the person who stayed. Person A owes $363.00 + $1,045.00 = $1,408.00; Person B owes $242.00; together $1,650.00, exactly the three bills. Applying 60/40 to the whole month instead would give $990.00 and $660.00, overcharging Person B by $418.00 for 19 days they no longer lived there.
In the next full period there is no shared stretch at all. Each person has their own address and their own bills, so the shared part is zero and nothing is divided.
| Bill | Person A | Person B |
|---|---|---|
| Rent | $1,500.00 | $920.00 |
| Electric | $54.00 | $31.00 |
| Internet | $60.00 | $45.00 |
| Total | $1,614.00 | $996.00 |
Person A owes $1,500.00 + $54.00 + $60.00 = $1,614.00. Person B owes $920.00 + $31.00 + $45.00 = $996.00. Together $2,610.00 for the two homes. The shared part is $0.00, so no share or divisor is used anywhere on this table. These are example values set by this page.
| Measure | Example 1 | Example 2 |
|---|---|---|
| Shared days | 11 | 0 |
| Shared part | $605.00 | $0.00 |
| Own part | $1,045.00 | $2,610.00 |
| Bills total | $1,650.00 | $2,610.00 |
Both examples close: shared part plus own part equals the bills total. The only thing that changes between them is the number of shared days. Once it reaches zero, the split disappears and the two lists stand alone.
For one bill that covers the whole period, shared part = bill × shared days ÷ period days, and own part = bill × own days ÷ period days. Shared days plus own days equal the period days, so the two parts always add back to the bill. Divide the shared part by the shares the two people used before the change; assign the own part in full to the person who stayed. The two amounts owed then add back to the bill, with nothing counted twice and nothing left over.
Only bills whose period straddles the change need this cut. A bill that ends before the day they stopped sharing is shared in full; one that starts after it belongs to whoever stayed, in full. A bill at a new address belongs to that person alone from the start. The day split here is a page setting used to show the arithmetic: 30 days, 11 shared, 19 alone. It is not a statement about any lease, any notice period or any legal definition of when a home stops being shared.
Splitting by days is an assumption this page makes about its own example bills, not a rule about how utilities charge. A real electricity bill follows a meter, a real rent charge follows the lease, and a fixed internet fee does not move with days at all. The examples use a straight day cut so every figure can be checked with multiplication and division alone. Where the real bill is not proportional to days, use the amount on the bill for each stretch instead of the day ratio.
Each amount on this page is an example value set by this page, and each one is accounted for here.
Bill totals and the period. The $1,500.00, $90.00, $60.00, $920.00, $54.00, $31.00 and $45.00 figures, the 30-day period, the Day 12 change and the 11 / 19 day split are example values set by this page. No bill, lease, meter or statement was read.
The shares. The 60/40 division of the shared part is an example share set by this page. It is not a default, a recommendation or a rule from anywhere.
Parts, amounts owed and totals. Each is worked arithmetic from the figures above, using multiplication, division, addition and subtraction only; no measurement.
There is no source to cite for any of these numbers and none is quoted - they are worked arithmetic, not published figures. For a real household, the bill amounts come from your own statements, the period from the dates on them, the day the home stops being shared from your own arrangement, and the shares from whatever the two of you agreed before the change. This page reports no average bill, no typical share, no legal rule and no official rate of any kind: no single published figure applies to every household, and none was found that could be quoted here.
Every other page here divides money between people who share one bill. Roommate Agreement covers what happens when one roommate leaves and the split has to be recomputed for the people still in the same home. Cost Splitter settles one shared cost against what each person already paid. Monthly Household Bill Calculator divides a month of household bills per person, and Split Bills Between Paychecks groups bills by which paycheck funds them. Prorated Rent Calculator works out one tenant's partial-month rent against a landlord. This page is about a boundary in time: which stretch of one bill period is still shared, and which stretch belongs to one person alone. It does not decide who should move, who stays on a lease or what anyone is legally entitled to.
This page is a worked method with two examples. It is not legal, financial or family advice, does not define separation or decide what it means for a lease, a tenancy or a shared account, and does not say who must pay which bill. It connects to no bank, employer, landlord or billing account, moves or holds no money, and stores nothing. It does not quote any price, average, rate, statute or official figure. It also does not handle a bill that arrives after the change but covers an earlier stretch, a deposit held at the old address, or a bill whose amount does not follow days - those need the real figures from the statements and the lease, not a worked example.