Guide BMD

How does a tontine work? The clear and complete guide

Millions of people rely on it, yet almost no one explains it correctly. Here’s how a tontine really works — and what causes it to fail.

The BMD editorial team·14 juillet 2026·3 min read

A tontine is a rotating fund. A group of trusted individuals contributes the same amount, at the same frequency. At each round, the entire pot goes to one member — just one. In the next round, it goes to another. And so on until everyone has received their turn.

That's it. The mechanism can be summed up in three lines. Its strength lies not in its complexity: it lies in what it enables.

What a tontine really solves

Saving alone is difficult. Not because of a lack of discipline, but because nothing compels us to do so. A tontine transforms a personal intention into a collective commitment: you do not contribute for yourself, you contribute for the person whose turn it is. Not paying is no longer just disappointing yourself — it’s defaulting in front of others.

It also solves something that banks cannot do: provide a significant sum to someone without guarantees. The first person served receives a capital that would have taken them months to gather. The last has saved, like a savings account. In between, everyone benefits.

The two main types

There are two ways to decide who receives, and when. This is the only real difference between tontines around the world.

• The order is set in advance. By drawing lots, seniority, or agreement. Everyone knows from the start when their turn comes. This is the most common form — the one called njangui in Cameroon, natt in Senegal, susu in Ghana.
• The order is contested through auctions. At each round, the person who needs money the most immediately agrees to receive a little less to go ahead. The reduction they accept is redistributed to others. This is the principle of the Asian hui.

The second form is more subtle than it seems: it puts a price on urgency. Those who can wait are rewarded for their patience. Those who cannot pay for priority — but they pay their friends, not a bank.

The real risk, and it’s not where you think

It is often imagined that the danger of a tontine is theft. This is rarely the case. The real risk, the one that causes groups to collapse, is more mundane: someone stops contributing after having been served.

The mechanics are relentless. The first person served has received the entire pot while having only contributed once. As long as they contribute until the end, the balance holds. If they disappear, it is the last on the list — those who have contributed the most and received the least — who lose.

A tontine does not die from theft. It dies from a forgetfulness that sets in, followed by a silence that no one dares to break.

The second risk is that of the ledger. For generations, the tontine has been kept in a notebook, with the treasurer. A notebook can be lost, damaged, or disputed. And when two people remember a payment differently, there is no referee — there are only two testimonies.

What truly protects a group

• A record of each payment, timestamped, that no one can rewrite afterward.
• A known order of passage for everyone from the start, and a history of changes when there are any.
• Reminders that do not depend on the courage of the treasurer: it’s the system that reminds, not a person who must dare to ask.
• A clear rule, decided before the first round, on what happens if someone defaults.

None of this is new: good groups have been doing it forever. The difference is that a tool does not tire, does not crumple, and does not have selective memory.