Proration

A tenant moves in halfway through the month, and their first invoice isn't a round month's rent. That's proration — REDA charging only for the days the tenant actually occupies a partial period. This article shows you exactly how REDA works out a prorated amount, so you can reproduce any move-in or move-out figure by hand and answer the classic front-desk question: "why is my first invoice 1,161.29 and not a full month?" There are two calculation conventions, a full-month safeguard, and a couple of preview fields that show the numbers before any invoice exists. No accounting background is assumed.

When REDA prorates

Proration kicks in on recurring charges — rent and other repeating charges — that have Do Prorate switched on, and only for a partial period. A partial period is one where the tenant doesn't have the whole billing window: the first period when a lease starts mid-month, or the last period when it ends mid-month. Full months in between are billed in full.

Proration applies to recurring charges only. If you try to switch it on for a one-time charge, REDA stops you:

The same rule holds on the fee templates that generate charges (admin charge setups), where the message reads:

The same calculation engine also runs in a few other places — month-to-month holdover fees, straight-line schedules, and inflation catch-up invoices — so the two conventions below govern those too.

One subtlety worth naming: REDA prorates the period the tenant actually holds, which it clamps to the lease. A billing window never starts before the charge's from date or the lease start, and never runs past the charge's to date or the lease end. That's precisely why a month you'd call "full" can still prorate — if the lease started or ended inside it, only part of the month falls within the clamped window.

The 30-day-month switch

There are two philosophies for turning a monthly rent into a daily rate, and your Leasing Rule picks one for the whole lease:

Neither is "more correct" — they're policy choices. The 30-day convention makes every day worth the same across the year; the actual-days convention ties each day to its own month. You set the convention once per Leasing Rule, and it applies to every partial period that lease bills.

The math, worked both ways

Here's the calculation, using the demo lease throughout: Aisha Rahman at Meridian Court #101, monthly rent 1,200.00, Do Prorate on. She moves in on 2 January, so the first period covers 2–31 January — 30 days of a 31-day month.

Always do it in two steps: find the daily rate, then multiply by the days occupied.

So the very same 30-day stay produces 1,200.00 under the 30-day convention and 1,161.29 under actual days — because January's daily rate is smaller when spread over 31 real days.

Full months are never shortchanged

The 30-day convention raises an obvious worry: if every month is "30 days," does February — which has 28 — get billed for only 28/30ths? No. A full month always bills the full amount. The 30-day divisor only ever applies to a partial period; a complete month bills its complete rent.

So in Aisha's lease, February bills 1,200.00 flat under either convention. The divisor only touches the stub periods at the start and end of the lease.

Weekly and daily charges

Not everything is monthly. The same logic scales to other charge periods:

Previewing the stub on the charge

You don't have to wait for an invoice to see the prorated figures. When you save a prorating charge, REDA computes and displays two preview fields on the charge itself:

• First Period Prorated Amount — what the opening stub period will bill.
• Last Period Prorated Amount — what the closing stub will bill when the lease ends.

These let you confirm the move-in and move-out amounts up front, before any invoice is generated.

A recurring rent charge with Do Prorate switched on: the first-period prorated amount is filled in for the partial move-in month, while the last-period field stays blank because this lease ends on a full month.

The prorated first-month invoice: instead of a full 1,200.00, the tenant is billed only for the days actually occupied — here 1,161.29 for a move-in partway through the month. The next month then bills the full 1,200.00.

Where the same math reappears

Proration isn't only a move-in story. The same daily-rate calculation, honoring the same 30-day-month switch, runs anywhere REDA has to bill a partial slice of a period:

Because they all share one engine, the amount you compute by hand for a move-in stub is the same amount those features would produce for their equivalent partial period — the convention you set on the Leasing Rule carries through every one of them.

Worked example: Aisha's first month, both ways

Putting it together for Aisha Rahman — Meridian Court #101, rent 1,200.00/month, move-in 2 January, first period 2–31 January (30 days):

The Last Period Prorated Amount works the same way from the other end: if Aisha gives notice and moves out part-way through a month, that closing stub prorates by the identical formula.

Where to go next

1. How Recurring Invoicing Works — where the prorated first and last invoices actually appear.
2. Invoices Explained — reading the prorated invoice, field by field.
3. Month-to-Month Fees — where the same proration runs on holdover fees.
4. Straight-Line Rent — proration inside averaged rent schedules.
5. Inflation Adjustments — catch-up invoices that prorate the difference.

Frequently asked questions