Rethinking Shared Expenses for Events
One of the most friction-prone aspects of organizing any group event is managing money. Who paid for what? How do you split costs fairly when not everyone participated in every activity? How do you handle multiple currencies during an international trip?
In Play The Event, the expense management module was designed from scratch to solve these problems with a flexible, intelligent system that adapts to any scenario.
What You Will Learn in This Article
- The four smart splitting modes: Equal, Percentage, Fixed, and Custom
- Multi-currency support and automatic conversion
- Settlement tracking and balance resolution
- Receipt tracking and document management
- Excel export with Univerjs spreadsheet integration
- The domain model behind the expense engine
Four Smart Splitting Modes
The core insight behind the expense system is that not all expenses are created equal. A dinner for the whole group should be split differently from a taxi ride shared by three people. Play The Event provides four distinct splitting strategies, each modeled as a first-class concept in the domain layer.
1. Equal Split
The simplest and most common mode. The total amount is divided equally among all selected participants. This is ideal for shared meals, venue rentals, or group transportation where everyone benefits equally.
EXPENSE: Restaurant dinner
TOTAL: EUR 180.00
PARTICIPANTS: 6 people
SPLIT MODE: EQUAL
RESULT:
├── Alice: EUR 30.00
├── Bob: EUR 30.00
├── Charlie: EUR 30.00
├── Diana: EUR 30.00
├── Eve: EUR 30.00
└── Frank: EUR 30.00
PAID BY: Alice (EUR 180.00)
ALICE IS OWED: EUR 150.00 from the group2. Percentage Split
When costs should be distributed proportionally rather than equally, the percentage mode allows organizers to assign a specific percentage to each participant. The system validates that all percentages sum to exactly 100%.
When to Use Percentage Split
- Corporate events where departments contribute different shares
- Group trips where some participants have higher budgets
- Shared accommodation split by room size or occupancy
3. Fixed Amount Split
In this mode, each participant is assigned a specific fixed amount. The system validates that all fixed amounts sum to the total expense. This is useful when exact amounts are known in advance, such as pre-ordered items at different price points.
4. Custom Split
The most flexible option, the custom split allows complete freedom in assigning amounts. Organizers can mix and match, assigning different values to different participants based on consumption, preference, or any other criterion. The system handles rounding differences and ensures the total always balances.
EXPENSE: Group activity day
TOTAL: EUR 250.00
SPLIT MODE: CUSTOM
ASSIGNMENTS:
├── Alice: EUR 80.00 (kayaking + lunch)
├── Bob: EUR 45.00 (lunch only)
├── Charlie: EUR 80.00 (kayaking + lunch)
└── Diana: EUR 45.00 (lunch only)
SUBTOTAL: EUR 250.00 (validated)
PAID BY: Charlie (EUR 250.00)Multi-Currency Support
International events introduce the challenge of handling expenses in different currencies. A weekend trip across borders might involve payments in euros, pounds, and local currencies. Play The Event addresses this with a built-in multi-currency engine.
Each expense records the original currency of the transaction. The system maintains exchange rates and performs automatic conversions when calculating balances. Participants can view their totals in any supported currency, and the settlement algorithm always produces the minimum number of transfers needed to resolve all debts.
Design Decision: Currency at the Expense Level
Rather than forcing a single currency per event, each individual expense can have its own currency. This mirrors real-world behavior where travelers pay in local currencies at different stops. The Money value object in the domain layer encapsulates both the amount and the currency code, ensuring type safety throughout the system.
Settlement Tracking
After all expenses have been recorded, the settlement engine calculates the optimal set of transfers to resolve all debts. The algorithm minimizes the total number of transactions required, avoiding circular payments.
SETTLEMENT CALCULATION
STEP 1: Calculate net balance for each participant
├── Alice: paid EUR 180, owes EUR 110 → net +70
├── Bob: paid EUR 0, owes EUR 95 → net -95
├── Charlie: paid EUR 250, owes EUR 155 → net +95
└── Diana: paid EUR 50, owes EUR 120 → net -70
STEP 2: Generate minimum transfers
├── Bob → Alice: EUR 70 (settles Alice)
├── Bob → Charlie: EUR 25 (partial settle)
└── Diana → Charlie: EUR 70 (settles both)
RESULT: 3 transfers instead of 6 individual reimbursementsEach settlement can be marked as pending, completed, or disputed. Participants confirm when they have sent or received a payment, providing a clear audit trail for the entire group.
Receipt Tracking and Document Management
Every expense in Play The Event can have one or more receipts attached. Participants snap a photo of the receipt, upload it directly through the mobile interface, and it is permanently linked to the expense record.
This feature is particularly valuable for corporate events where expense reports require documentation, and for group trips where disputes about who paid for what can be resolved instantly by consulting the attached receipt.
Receipt Management Features
- Photo upload directly from mobile camera
- Multiple receipts per expense
- Automatic association with the expense record
- Viewable by all event participants for transparency
- Included in the Excel export for accounting purposes
Excel Export with Univerjs Integration
For organizers who need to share financial summaries outside the platform or integrate with accounting workflows, Play The Event offers a comprehensive Excel export. But the integration goes further: a Univerjs-powered spreadsheet is embedded directly within the application, allowing real-time editing and collaboration without leaving the platform.
The Univerjs spreadsheet component provides a familiar Excel-like interface where organizers can view, filter, and manipulate expense data. Formulas, sorting, and conditional formatting are all supported, giving power users the flexibility they need while keeping everything within a single ecosystem.
EXCEL EXPORT - SHEETS
Sheet 1: EXPENSE SUMMARY
├── Date | Description | Amount | Currency | Paid By | Split Mode
├── Totals per participant
└── Grand total
Sheet 2: BALANCES
├── Participant | Total Paid | Total Owed | Net Balance
└── Settlement status
Sheet 3: SETTLEMENTS
├── From | To | Amount | Currency | Status | Date
└── Overall settlement progress
Sheet 4: RECEIPTS
├── Expense | Receipt URL | Upload Date | Uploaded By
└── Document referencesThe Domain Model
Behind the user-facing features lies a carefully designed domain model. The expense system revolves around several key entities and value objects that enforce business rules at the domain level.
The Expense entity serves as the aggregate root, containing references to the split strategy, the payer, the list of participants with their shares, and any attached receipts. The split strategy is implemented using the Strategy pattern, allowing the system to swap between Equal, Percentage, Fixed, and Custom splitting without modifying the core expense logic.
Immutability and Audit Trail
Once an expense is finalized and settlements have begun, the expense record becomes immutable. Any corrections require creating an adjustment expense rather than modifying the original. This design ensures a complete audit trail and prevents disputes caused by retroactive changes.
Key Takeaways
Lessons from Building the Expense Module
- Flexibility over simplicity: Four splitting modes cover virtually every real-world scenario without overcomplicating the UI
- Currency is a first-class concept: Embedding currency in a value object prevents entire categories of bugs
- Minimize settlements: The optimal transfer algorithm dramatically reduces friction in the repayment process
- Receipts build trust: Attaching proof of payment eliminates the most common source of group expense disputes
- Embedded spreadsheets: Univerjs integration bridges the gap between structured data and the flexibility users expect from Excel
In the next article, we will explore how Play The Event handles trip planning with multi-stop itineraries, external API integrations, and interactive maps.