The three proration methods, and why it matters which one you pick
There is no single legally mandated way to prorate rent in most states. That freedom is exactly the problem: you and your tenant can each do honest arithmetic and reach different numbers, because you divided by different things.
| Method | Daily rate on $1,500 rent | 14 days would cost |
|---|---|---|
| Actual days in that month (30-day month) | $50.00 | $700.00 |
| Actual days in that month (31-day month) | $48.39 | $677.42 |
| Flat 30-day month, every month | $50.00 | $700.00 |
| Annualised — rent × 12 ÷ 365 | $49.32 | $690.41 |
The spread between the highest and lowest method on a single mid-month move-in is about $23 here. Small — until it is the reason a tenancy starts with an argument. The calculator above uses the real number of days in the month you select, which is the most common and the easiest to defend, because it is the only one that matches the calendar the tenant is looking at.
When do you prorate?
- Move-in after the 1st — the classic case, and the one the calculator is built for.
- Move-out before the end of the month, where the lease or your state's rules entitle the tenant to a refund of the unused days.
- A rent increase taking effect mid-month — prorate the old rate and the new one, and show both lines.
- A lease that starts late because the unit was not ready. Prorate from the day you actually delivered possession, not the day the lease was signed.
One case where you should not prorate silently: a tenant who leaves early without the right to. Refunding the unused days looks generous and is often read as accepting the early termination. Deal with the break in writing first, then work out the money.
Prorating the first month when a deposit is also due
At move-in the tenant usually pays three things at once: the prorated first month, the security deposit, and sometimes the last month's rent. Give them one written statement showing the three lines separately and the total, and keep a copy.
This matters more than it looks. In most states the deposit cap counts everything you hold as security — a last month's rent held in reserve, a pet deposit, a key deposit — not just the line labelled "security deposit". If those amounts are blurred into one payment, you cannot later show that you stayed under your state's cap.
Check your own state's ceiling before you take the money, and keep the receipt itemised.
How to record it so it does not confuse your books
A prorated first month breaks a naive rent ledger: the amount does not match the lease, so a year later it looks like a shortfall. Record it as a rent payment of its own with a note saying what period it covers, not as a partial payment against a full month.
Rentmark handles this automatically — the first rent schedule of a lease is generated for the real period between the start date and the first full month, at the prorated amount, so the ledger reconciles and the receipt says exactly which days were paid for.