Lease Rent Schedule
The shared calculator in @parcelis/schemas plans monthly rent charges for a fixed lease term. The API and lease preview can use the same result. It does not write invoices; invoice persistence belongs to the lease finalization flow.
Calendar periods and due dates
Pass monthlyRentCents, rentDueDay, and inclusive startsOn and endsOn dates to calculateMonthlyRentSchedule. The lease dates use YYYY-MM-DD calendar strings. The organization's timezone applies when a due date is converted to an instant or compared with today. A lease must start and end in different calendar months.
The result contains one period for each month touched by the lease. A partial month costs monthly rent × occupied days ÷ days in month, rounded to cents. Rent due days beyond the end of a month use that month's last day. If the first month's due day has passed, its rent is due on the lease start date. A partial final month is due on the lease end date.
For a $1,200 monthly lease from April 16 through June 15, due on the 1st, the periods are:
| Period | Rent | Due date |
|---|---|---|
| April 16–30 | $600 | April 16 |
| May 1–31 | $1,200 | May 1 |
| June 1–15 | $600 | June 15 |
Tenant charges
Pass a period and the lease's billing responsibility, tenant IDs, and saved monthly rent allocations to planMonthlyRentCharges.
- Joint billing produces one charge with every tenant as a recipient.
- Individual billing produces one charge per tenant. Partial rent uses each tenant's monthly share; any rounding cents go to the largest fractional remainders, with tenant ID breaking ties. The charges always total the period rent.
Each plan has a rent sourceKey for its calendar month and liable tenant or joint group. Invoice persistence must scope the key to the lease and enforce uniqueness, while deposits and other charges use distinct identities.