A tenant moves in on the 12th. The rent cycle runs on the 1st. They owe something for September, and it is not the full month.
Pro-rating is the arithmetic that produces that number. It is simple, it is disputed constantly, and it is disputed for one reason: the calculation is almost never shown.
The two methods
Actual days in the month. Monthly rent divided by the number of days in that specific month, multiplied by days occupied.
KES 36,000 in September, 30 days. Daily rate KES 1,200. Moving in on the 12th means 19 days occupied, so KES 22,800.
A fixed 30-day month. Monthly rent divided by 30 regardless of the actual month, multiplied by days occupied.
The same tenancy starting 12 February, in a 28-day month: the actual-days method gives a daily rate of KES 1,285.71 and 17 days of KES 21,857. The fixed-30 method gives KES 1,200 and KES 20,400.
Neither is wrong. They give different answers, and the one your tenancy uses should be the one written in the tenancy agreement.
Show the working, always
A pro-rata charge that arrives as "Rent (part month): 22,800" gets questioned nearly every time, even when it is exactly right, because the tenant has no way to check it and the figure does not match the one in their agreement.
The same charge shown as "Rent 12 to 30 September, 19 days at 1,200 per day: 22,800" is questioned almost never. The cost of the second version is one line.
Where else it applies
Pro-rating is not only a move-in problem:
- Move-out mid-period, where the tenancy ends before the cycle does.
- Service charge and recurring items, which need the same treatment and are frequently charged in full by accident.
- A rent review taking effect mid-period, which produces a bill at two rates and should show both.
- Utilities, which are usually consumption-based and so pro-rate themselves, except for standing charges, which do not.
The move-in that is not pro-rated
One case causes recurring confusion. Many Kenyan tenancies count notice and rent from the first of the following month rather than from the day of occupation. Where that is the arrangement, a tenant moving in on the 12th may owe the balance of September and a full October, and there is no pro-rating at all.
That is a legitimate arrangement and it is not what most tenants expect. It belongs in the agreement, stated plainly, and confirmed in writing before anybody moves anything.
What goes wrong
Only rent is pro-rated. Service charge, parking and the security levy are charged in full for a unit occupied for a third of the month, because the run pro-rates the rent line and nothing else.
The method is inconsistent. Actual days one month, thirty-day convention the next, depending on who processed it. Two tenants with identical circumstances get different bills.
It is done by hand. A manual proration in a portfolio of two hundred units is a transcription error waiting for a month with a move-in on the 29th.