@zenuinebit/rent-schedule

Rent for a lease month by month, with proration, yearly increases, payments, late fees and deposit settlement. Amounts are integers in minor units (see @zenuinebit/money). Dates are "YYYY-MM-DD" strings.

import { schedule, applyPayments, lateFee, settleDeposit } from "@zenuinebit/rent-schedule";

const lease = schedule({
  startDate: "2025-01-15",
  months: 11,                                    // or endDate: "2025-12-14"
  monthlyRent: 2_500_000,                        // 25,000.00 in minor units
  dueDay: 5,
  escalation: { percent: 5, everyMonths: 12 },   // optional
});
lease.rows;   // [{ number, periodStart, periodEnd, days, dueDate, monthlyRent, prorated, amount }]
lease.total;

const ledger = applyPayments(lease.rows, [{ date: "2025-01-15", amount: 2_500_000 }]);
ledger.rows[0].status;   // "paid" | "partial" | "unpaid"
ledger.outstanding;      // unpaid rent
ledger.credit;           // paid in advance

lateFee({ amountDue: 2_500_000, dueDate: "2025-03-05", paidDate: "2025-03-12" },
        { graceDays: 3, flat: 50_000, perDay: 10_000, cap: 200_000 });
// { daysLate: 4, fee: 90000 }

settleDeposit(5_000_000, [{ reason: "Repainting", amount: 800_000 }]);
// { deducted: 800000, refund: 4200000, shortfall: 0 }

How it works

• Rent is billed per calendar month. A first or last month that is only partly covered is prorated by days: rent x days / days in that month, rounded to the minor unit.
• Escalation happens at the start of every Nth billing period and compounds on the previous rounded rent, so a lease that starts mid-month increases on a month boundary, not on the anniversary.
• applyPayments pays the oldest rent first and splits one payment over several months if needed.
• lateFee counts days after the grace period. Flat and percent fees apply once the payment is late; per-day fees grow daily; cap limits the total.
• Dates are plain calendar dates, so there are no time-zone surprises.

Not included: interest on late rent, tax or TDS on rent, maintenance charges, and rent-control limits. Your lease terms and local law decide those.