An open-source, offline, and lightweight AI-powered billing and transaction management system with natural-language question answering and voice assistance.
BillMind AI helps users manage invoices, expenses, payments, customers, vendors, and transaction records. Users can ask questions in simple language and receive clear answers based on stored billing data.
The goal of BillMind AI is to create an intelligent billing system that allows users to:
- Create and manage invoices
- Record sales and purchases
- Track payments and receipts
- Monitor pending balances
- Manage customers and vendors
- Search transactions using natural language
- Ask questions about billing records
- Receive spoken answers
- Detect duplicate or suspicious transactions
- Generate financial summaries and reports
The project will initially use rule-based AI, retrieval systems, symbolic reasoning, and structured data processing instead of depending on large language models or paid external APIs.
User:
How much payment is pending from Sharma Traders?
BillMind AI:
Sharma Traders has an outstanding balance of ₹18,500 across three unpaid invoices.
User:
How much did I spend on materials this month?
BillMind AI:
Your recorded material expenses for this month are ₹46,200.
User:
Which invoices are overdue?
BillMind AI:
Four invoices are overdue. Their combined pending amount is ₹32,750.
User:
When was the ₹25,000 transaction recorded?
BillMind AI:
The ₹25,000 payment was recorded on 18 July 2026 for electrical material purchase.
- Create sales invoices
- Create purchase invoices
- Generate invoice numbers
- Add products and services
- Calculate subtotal, tax, discount, and total
- Track invoice status
- Store due dates
- Export invoices
- Maintain invoice history
- Record income
- Record expenses
- Record payments
- Record receipts
- Store transaction date and time
- Add categories and notes
- Link transactions with invoices
- Search transaction history
- Track payment methods
- Store customer details
- Track customer invoices
- Track received payments
- Calculate outstanding balance
- View customer transaction history
- Maintain customer notes
- Store vendor details
- Track purchase bills
- Record vendor payments
- Calculate pending payable amount
- View vendor transaction history
- Maintain supplier records
- Record business expenses
- Categorize expenses
- Track recurring expenses
- Add supporting bill references
- Generate daily and monthly summaries
- Compare expense categories
- Track fully paid invoices
- Track partially paid invoices
- Track unpaid invoices
- Record payment method
- Generate payment receipts
- Calculate pending balances
- Maintain payment history
BillMind AI will answer questions using stored billing and transaction records.
Supported question categories may include:
- Invoice totals
- Pending payments
- Customer balances
- Vendor balances
- Daily expenses
- Monthly expenses
- Sales totals
- Purchase totals
- Transaction dates
- Payment methods
- Overdue invoices
- Highest expenses
- Recent transactions
- Tax summaries
- Profit and loss estimates
- Convert answers into speech
- Work offline
- Support simple voice commands
- Repeat previous answers
- Provide short spoken summaries
- Support billing-specific vocabulary
BillMind AI will initially use a lightweight and explainable AI architecture.
The system may include:
- Text normalization
- Keyword extraction
- Intent detection
- Entity extraction
- Date and amount recognition
- Rule-based reasoning
- Database retrieval
- Mathematical calculations
- Response templates
- Context memory
- Confidence scoring
Example processing pipeline:
User Question
↓
Text Normalization
↓
Intent Detection
↓
Entity Extraction
↓
Billing Database Search
↓
Calculation and Reasoning
↓
Response Generation
↓
Offline Text-to-Speech
Question:
How much does Amit still need to pay?
Extracted information:
Intent: customer_pending_balance
Customer: Amit
Time range: all records
Processing:
Total invoice amount: ₹45,000
Total payment received: ₹30,000
Pending balance: ₹15,000
Generated response:
Amit still needs to pay ₹15,000.
billmind-ai/
│
├── src/
│ ├── assistant/
│ │ ├── question_parser.py
│ │ ├── intent_detector.py
│ │ ├── entity_extractor.py
│ │ ├── reasoning_engine.py
│ │ ├── query_engine.py
│ │ └── response_generator.py
│ │
│ ├── billing/
│ │ ├── invoices.py
│ │ ├── invoice_items.py
│ │ ├── payments.py
│ │ ├── receipts.py
│ │ ├── taxes.py
│ │ └── discounts.py
│ │
│ ├── transactions/
│ │ ├── income.py
│ │ ├── expenses.py
│ │ ├── purchases.py
│ │ ├── sales.py
│ │ └── categories.py
│ │
│ ├── contacts/
│ │ ├── customers.py
│ │ └── vendors.py
│ │
│ ├── reports/
│ │ ├── sales_report.py
│ │ ├── expense_report.py
│ │ ├── payment_report.py
│ │ ├── tax_report.py
│ │ └── profit_loss_report.py
│ │
│ ├── memory/
│ │ ├── billing_memory.py
│ │ ├── conversation_memory.py
│ │ └── knowledge_store.py
│ │
│ ├── voice/
│ │ ├── speech_input.py
│ │ └── speech_output.py
│ │
│ ├── database/
│ │ ├── connection.py
│ │ ├── schema.py
│ │ └── repositories.py
│ │
│ └── interface/
│ ├── cli.py
│ ├── desktop_app.py
│ └── web_dashboard.py
│
├── data/
│ ├── invoices/
│ ├── transactions/
│ ├── customers/
│ ├── vendors/
│ └── reports/
│
├── tests/
├── documentation/
├── examples/
├── scripts/
├── LICENSE
├── CONTRIBUTING.md
├── ROADMAP.md
└── README.md
Create the core billing data system.
- Customer records
- Vendor records
- Product and service records
- Invoice records
- Invoice item records
- Payment records
- Receipt records
- SQLite database
Build the transaction management engine.
- Income tracking
- Expense tracking
- Sales tracking
- Purchase tracking
- Transaction categories
- Payment methods
- Transaction search
- Balance calculations
Create the complete invoice workflow.
- Invoice creation
- Automatic invoice numbering
- Tax calculation
- Discount calculation
- Partial payment support
- Due-date tracking
- Invoice status updates
- Invoice export
Create the natural-language question-processing system.
- Text normalization
- Keyword extraction
- Intent detection
- Customer and vendor recognition
- Amount recognition
- Date recognition
- Invoice number recognition
- Question validation
Build the rule-based reasoning system.
- Pending balance calculation
- Invoice total calculation
- Customer balance calculation
- Vendor payable calculation
- Expense summaries
- Sales summaries
- Overdue invoice detection
- Transaction comparison
- Confidence scoring
Generate understandable billing answers.
- Response templates
- Hinglish response support
- Short answer mode
- Detailed answer mode
- Missing-data responses
- Explainable calculation output
- Follow-up question support
Allow BillMind AI to speak answers.
- Offline text-to-speech
- Voice selection
- Speech queue
- Repeat command
- Stop command
- Number and currency pronunciation
Allow users to ask billing questions by speaking.
- Offline speech recognition
- Voice command detection
- Number recognition
- Customer-name recognition
- Noise handling
- Billing vocabulary support
Create a simple billing interface.
- Sales dashboard
- Expense dashboard
- Invoice dashboard
- Customer dashboard
- Vendor dashboard
- Payment dashboard
- Search and filters
- Financial summary cards
Add financial reports and basic analytics.
- Daily sales report
- Monthly sales report
- Expense report
- Outstanding balance report
- Customer ledger
- Vendor ledger
- Tax summary
- Profit and loss estimate
- Cash flow summary
Create transaction warning systems.
- Duplicate transaction detection
- Duplicate invoice detection
- Unusual payment alerts
- Missing payment reference warnings
- Suspicious expense patterns
- Unexpected balance changes
- Overdue payment alerts
Prepare the first stable release.
- Complete testing
- Documentation
- Sample billing dataset
- Backup and restore system
- Data export
- Performance optimization
- Installation package
- Privacy and security review
The initial version may use:
- Python
- SQLite
- HTML
- CSS
- JavaScript
- Standard Python libraries
- Custom rule-based AI
- Lightweight offline speech components
The project aims to avoid unnecessary heavy dependencies and remain usable on regular computers.
Billing records should remain accessible without an internet connection.
Customer, vendor, invoice, and transaction data should remain under the user’s control.
The software should run on low-end and CPU-based computers.
Every AI-generated answer should show which records and calculations were used.
Financial calculations should be deterministic, testable, and traceable.
Billing, transactions, AI, voice, reports, and interfaces should remain separate modules.
BillMind AI should work for multiple domains, including:
- Construction
- Retail shops
- Freelancers
- Small businesses
- Contractors
- Service providers
- Local vendors
{
"invoice_number": "INV-2026-001",
"customer_name": "Sharma Traders",
"invoice_date": "2026-07-25",
"due_date": "2026-08-10",
"subtotal": 20000,
"tax": 3600,
"discount": 1000,
"total_amount": 22600,
"paid_amount": 10000,
"pending_amount": 12600,
"status": "Partially Paid"
}{
"transaction_id": "TXN-2026-0142",
"date": "2026-07-25",
"type": "Expense",
"category": "Construction Material",
"description": "Electrical wire purchase",
"amount": 25000,
"payment_method": "UPI",
"vendor": "Jaipur Electricals",
"invoice_reference": "PUR-2026-009"
}BillMind AI can work as the billing engine for BuildGuardian AI.
BuildGuardian AI
↓
BillMind API
↓
Invoices and Transactions
↓
Billing Reasoning Engine
↓
Answer
Example:
BuildGuardian AI Question:
How much has been paid to the electrician?
BillMind AI Response:
A total of ₹42,000 has been paid to the electrician across five recorded transactions.
This separation allows BillMind AI to remain useful outside construction projects while still supporting construction billing.
BillMind AI may be useful for:
- Small business owners
- Shop owners
- Freelancers
- Contractors
- Construction project owners
- Service providers
- Account assistants
- Local vendors
- Students learning billing systems
The project is currently in the planning and architecture stage.
Initial development will focus on:
- Customer and vendor data models
- Invoice and transaction database
- Basic billing calculations
- Command-line interface
- Rule-based question answering
- Offline response generation
Contributions are welcome.
You can contribute through:
- Billing feature development
- AI question-answering logic
- Database design
- Documentation
- Test cases
- Desktop or web interface
- Voice systems
- Financial report generation
- Security improvements
Before contributing, please read CONTRIBUTING.md.
- Keep financial calculations deterministic
- Add tests for all billing calculations
- Avoid unnecessary heavy dependencies
- Document important design decisions
- Never upload real customer financial data
- Use anonymized sample records
- Keep modules small and understandable
- Follow repository coding standards
Do not upload real bank account details, payment credentials, tax identification numbers, private customer information, or confidential transaction records to the public repository.
Use anonymized sample data for development and testing.
BillMind AI should not be treated as certified accounting, tax, or legal software without professional review.
This project is licensed under the MIT License.
See the LICENSE file for details.
BillMind AI aims to become a complete offline billing intelligence system that can manage invoices, understand transactions, answer financial questions, detect irregularities, and provide voice-based assistance.
The long-term vision is to create a lightweight Jarvis-like billing assistant for individuals, contractors, and small businesses.
Developed and maintained by the Dev Collaboration Hub community.