IOU Apps: The Complete Guide to Tracking Money Between Friends (2026)

What is an IOU app?

An IOU app tracks money that people owe each other. At its simplest, it replaces the mental note of "Alex owes me $40 for dinner." At its most powerful, it tracks dozens of shared expenses across a group, nets them all out, and calculates the minimum payments needed to settle up.

There are two categories of apps in this space:

• Expense trackers: Apps that record who paid what and calculate who owes whom. They do not move money. You settle up separately via Venmo, cash, bank transfer, or however you prefer.
• Payment apps: Apps like Venmo and Zelle that actually transfer money between accounts. They can request payments, but they do not maintain a running balance or help you split complex group expenses.

Most people need both: a tracker to figure out the amounts and a payment app to move the money. They serve different purposes.

The top IOU and expense tracking apps

Feature comparison: what matters most

Mutual confirmation

This is the single most important feature that most apps get wrong. In Splitwise, anyone in a group can add an expense and charge other people without their approval. This leads to disputes: "I did not agree to that" or "that amount is wrong."

Nudj requires both sides to confirm every expense. The person who paid logs it. The person who owes confirms it. Until both agree, it does not affect the balance. This eliminates surprise charges and builds trust.

Running balances

The best IOU apps maintain a running balance between you and each friend. If you paid for dinner last week ($40) and they paid for coffee today ($12), the net balance should show they owe you $28. This running ledger means you do not need to settle after every single expense.

Group expense splitting

For trips, roommates, and group events, you need to track expenses across multiple people. Key features to look for:

• Uneven splits: Not every expense is divided equally. Some apps let you assign custom amounts per person.
• Partial groups: When only 3 of 6 people participate in an activity, the expense should only split among those 3.
• Minimum settlements: When the trip is over, the app should calculate the fewest transfers needed to settle everyone. Without this, you end up with a spaghetti of payments going in every direction.

Payment integration

Some apps let you pay directly through the app. Others (like Nudj) focus purely on tracking and let you settle however you prefer. There is no right answer. In app payments are convenient, but they require linking bank accounts, which many people are not comfortable doing. A tracking only app has zero security risk because it never touches real money.

Common use cases

Roommates

Roommate expenses are ongoing: rent, utilities, groceries, household supplies. The best app for roommates tracks recurring expenses and maintains a running balance over months. You do not want to settle up after every grocery run. Instead, let the balance accumulate and settle monthly or quarterly.

Group trips

Trips generate dozens of expenses over a few days: accommodation, meals, activities, transportation. The key features here are group support, uneven splits (not everyone goes on every excursion), and minimum settlement at the end.

Poker nights and game nights

Poker nights have a unique structure: buy ins, rebuys, and cash outs. The net result for each player needs to be calculated, and then the losers need to pay the winners with the fewest transfers. Most expense apps do not handle this well. Nudj has a dedicated poker night mode built specifically for this use case.

Couples

Many couples track shared expenses, especially before they merge finances. Dinner, dates, shared subscriptions, groceries. A running balance between two people is the simplest version of expense tracking, and any of the apps above handle it well.

Why free matters

An IOU app only works if everyone in your group uses it. If the app costs money, some friends will refuse to sign up, and you are back to tracking in a spreadsheet or group chat. The best expense tracking apps are completely free for all users, with no features locked behind a paywall.

Splitwise's shift to freemium in 2023 pushed many users away because the free tier now includes ads and limits features. This is why many people search for a "free Splitwise alternative" and end up finding apps like Nudj, Tricount, and Settle Up.

How to choose the right app

Ask yourself three questions:

1. What is my main use case? Roommates need recurring expense support. Travelers need group splitting. Poker players need settlement calculators.
2. Does everyone need a paid account? If any member needs to pay, it is a dealbreaker for most groups.
3. Do I need payment processing or just tracking? If tracking is enough, choose a simpler app. If you want integrated payments, look at apps with Venmo or bank connections.

The bottom line

The best IOU app is the one your friends will actually use. It needs to be free, simple enough that everyone participates, and smart enough to handle your specific situation. Whatever you choose, using any app is infinitely better than relying on memory and group chat negotiations.