CosumSpend together. Keep the balance clear.
Available for iOS and Android.
How it works
The record, the split and the settlement stay connected.
- 1
Open a ledger
Name the trip or the flat, then add everyone by name. They do not need the app or an account.
Our flat
3 participants
- EEmmaYou
- NNoah
- MMaya
- 2
Add what was spent
The payer defaults to you, the split to the one you used last. Amount, done — under five seconds.
Dinner
Today
$120
- Payer
- Noah
- Included
- 3 people · equally
The payer and the split are saved as separate choices. - 3
Settle up
Cosum nets the balances and suggests the fewest payments that close the ledger. You decide when a real payment has happened.
Payment suggestion
OEmma
$40
İNoah
Cosum does not move money. It shows the payment that closes the balance.
Keep the payer accurate
One bill. Two payers. Two clear expense records.
Record what each person actually paid. Cosum works out the rest.
Worked example
Dinner · 3 people · split equally
Total recorded
$180
- 1
Dinner · part 1
Noah paid
$120
- 2
Dinner · part 2
Maya paid
$60
After each person’s $60 share
$60
One payment suggestion closes the balance. No money moves until the group pays in real life.
Why Cosum
Clear about what it does — and what it never does.
Cosum does
Keep the shared record understandable.
- Who paid and who was included, for every expense.
- Each participant's net balance, calculated automatically.
- The fewest payments needed to settle up.
Cosum does not
Pretend to be a bank or rewrite history.
- Never sends, receives or holds real money.
- No account or app required to participate.
- New participants never change past shares.
Joining needs no account
One person can keep the ledger for the whole group.
An expense in under five seconds
Useful defaults keep the form short without hiding the payer or split.
Opens without a signal
The last synced state stays visible and is clearly marked.
Questions worth answering
Know what will happen before the first expense.
The details that prevent a shared ledger from being misunderstood later.
Read the complete guideDoes everyone in a ledger need an account?
No. A participant can remain a name in the ledger. One person can add and manage expenses for the whole group, and others may join later if they want.
What if two people paid the same bill?
Add two expenses: one for the amount paid by the first person and one for the amount paid by the second. Each expense has exactly one payer, so the source of the money remains clear.
Why does Cosum suggest a payment between two people who never paid each other?
The suggestion is calculated from everyone’s net balance, not copied from transaction history. It reduces the number of payments needed to close the ledger.
Does Cosum send money when I mark a suggestion as paid?
No. Cosum does not connect to a bank or move money. It records a Transfer after the real-world payment has happened, then recalculates the balances.