Reducing balance vs flat rate: a worked example
On a KSh 1M, 12-month loan, the difference between the two is roughly KSh 90,000. Here is how to spot the trick in any loan offer.
Flat-rate interest charges you the headline rate on the original principal for the full tenor, even after you have paid most of it back. It is the oldest sleight of hand in lending, and it is still everywhere in Kenya because it lets a lender quote a rate that sounds reasonable while collecting roughly twice the interest a reducing-balance loan would.
Reducing balance, by contrast, recalculates interest each month against what you still owe. Pay early, pay less. There is no penalty for being responsible. If you settle the loan in month six, you only pay interest on the principal you actually held during those six months — not interest on a balance you cleared three months ago.
On a 12-month, KSh 1,000,000 loan at a stated 18% annual rate, flat rate costs roughly KSh 180,000 in total interest. Reducing balance, at the same stated 18%, costs roughly KSh 90,000. Same headline. Half the cost. The difference is not the rate. The difference is what the rate is being applied to each month.
The trick most borrowers miss is that flat-rate lenders quote a monthly rate that sounds tiny. '1.5% per month' feels reasonable until you realise it is charged every single month on the full original balance, not the declining one. Annualised on a reducing-balance basis, that 1.5% per month is closer to 33% APR. Twice what you thought you were paying.
A quick test you can run on any offer in under a minute: ask for the total interest paid over the life of the loan, divide it by the principal, then divide by the number of years of the loan. If that number is more than about 60% of the headline rate the lender quoted, you are looking at flat rate dressed up as something more respectable. If the lender refuses to give you a total-interest figure, that is the answer.
Our partner publishes the full amortisation schedule before you sign anything. You can see, month by month, how much of each instalment goes to interest and how much retires the principal. You can see the principal balance fall in real time. You can see the interest column shrink as that balance falls. If a lender will not give you that schedule, walk away. Anyone hiding the schedule is hiding the rate.
There is a second, subtler benefit of reducing balance that does not show up in the headline numbers: it rewards exactly the behaviour you want to encourage in yourself. Got a windfall in month four? Throw it at the loan and watch every subsequent instalment shrink. On flat rate, that windfall does almost nothing — you have already been charged the interest on the original balance for the full tenor.
We have run the comparison for hundreds of clients on the calculator on our site. The pattern is identical: borrowers who think they are getting a 'cheaper' flat-rate loan because the monthly payment is lower in month one are almost always paying more in absolute interest. The flat-rate monthly is lower because the principal repayment is smaller — meaning you carry the debt longer and pay interest on it for longer.
If you want to verify any of this independently, the Central Bank of Kenya publishes effective annual rate guidance and most reputable lenders disclose theirs. Compare effective annual rates, not monthly headline rates. A 1.5% monthly flat-rate loan and an 18% reducing-balance loan are not the same product, no matter how the brochure makes them look.
There is one situation where flat rate can be defensible: a very short, very small loan where the simplicity of a fixed total cost outweighs the difference in interest. We are talking three months, KSh 50,000 or less. For anything bigger or longer than that, reducing balance is structurally cheaper, structurally fairer, and structurally more aligned with the borrower behaving responsibly. Our partner offers reducing balance on every loan tenor, including the smallest.
The final test, and our favourite: ask the lender what happens if you clear the loan in full in month six of a twelve-month tenor. A reducing-balance lender will quote you the outstanding principal plus accrued interest for the days you held it. A flat-rate lender will, almost without exception, charge you most or all of the remaining interest anyway. That single question separates the honest products from the rest.