How Cost-Sharing Works in Kai: Splitting vs Reimbursing
Most groups think of cost-sharing as a single setting: "how do we split the costs?" In practice it is two separate controls, and keeping them apart is what makes a shared aircraft, yacht, vehicle, or property feel fair instead of fiddly.
- When a cost is shared, how is it divided between members?
- For any given expense, is it shared at all, or is the payer simply reimbursed?
Get both right and everyone's balance moves the way they expect after each expense.
How a shared cost is divided
This is the group-wide split method. You set it once, under Group settings, Financial, Expense sharing (the new Essentials page also offers a quick pick between Equal and Proportional for equal-partnership groups). It decides how any shared cost is spread across members:
- Equal. Evenly across all active members. A €200 fuel bill among four members is €50 each.
- Proportional to ownership. By each member's ownership percentage, or by share count if your group is share-based. If A holds 40% and B and C hold 30% each, a €1,000 cost becomes €400, €300, and €300.
- Don't split (owner pays). No automatic split. Expenses stay un-split, for groups where one member absorbs the costs and bills the others through their usage.
That is the whole of the split method. It is a property of the group, not of any single expense.
Whether an expense is shared at all
Here is the part groups miss. Not every cost should be split. Fuel you burned on your own trip is yours. A new set of sails is everyone's. So Kai decides sharing per expense, and how that works depends on whether your group uses invoicing.
- Invoicing groups. A member-paid expense defaults to reimbursing the payer in full. Nothing is split, and you get your money back. If the cost really is shared, an admin turns on "Split cost among members" on that expense, and it splits using the group's split method.
- Non-invoicing groups. Every expense is split among members automatically. There is no per-expense opt-out. If you want the "keep it on the payer" option, turn on invoicing (Essentials, Money, Invoicing).
- Paid by the group. For costs paid straight from the shared group account, no one is reimbursed, but members still owe their share to the group.
The default matters: in an invoicing group, adding an expense does not quietly bill everyone. It pays you back. Splitting is the deliberate choice.
A worked example
Say you hold 2 shares, three other owners hold 10 each, and the group uses invoicing with Proportional to ownership.
- You buy €120 of fuel for your own voyage. Leave "Split cost among members" off. Nothing is split: the group reimburses you the €120, and the cost of that voyage reaches you through your usage billing.
- The group replaces a €3,200 sail. Turn "Split cost among members" on. It splits by shares: your part is about €200 (2 of 32 shares) and each 10-share owner pays about €1,000.
Same group, same split method, two very different outcomes, because the split-or-reimburse choice went differently for each expense.
Where each one lives
- Split method (how a shared cost is divided): Group settings, Financial, Expense sharing, or the Essentials page under Money.
- Split vs reimburse (whether an expense is shared at all): the "Split cost among members" toggle on the expense form, in invoicing groups.
The short version
Set your split method once. Then, for each expense, decide whether it is shared. Personal costs stay with the person who paid; genuinely shared costs get split the way your group agreed. Two controls, set in two places, and nobody is surprised by their balance at the end of the month.
Want to see it on your own numbers? Demo at kai-sharing.com.
