I spent months building FLOW (vestelonflow.com) — a tool that analyzes bank statement PDFs and finds forgotten subscriptions, hidden fees, and recurring charges.
Here's what I learned building it in 8 languages.
The Problem
Most personal finance apps require you to connect your bank account. For many people (especially in Europe), that's a dealbreaker. GDPR concerns, privacy fears, and simply not trusting third-party apps with banking credentials.
My insight: the data people need is already in their PDF bank statements. Every bank generates them. Most people never look past the total.
The Tech Stack
The core flow:
- User uploads PDF bank statement
- PDF text extraction (pdfplumber + fallback OCR)
- Transaction parsing — this is the hard part
- LLM categorization pipeline
- Subscription detection (recurring charges with same merchant)
- Report generation
The trickiest part was transaction parsing. Every bank formats their PDF differently. German banks look nothing like Slovak banks. We ended up building bank-specific parsers for the most common formats and a fallback generic parser.
The 8-Language Challenge
Supporting Slovak, Czech, German, French, Spanish, Polish, Arabic, and Chinese wasn't just about translating the UI. The financial terminology varies significantly:
- "Permanent order" in English = "Trvalý príkaz" in Slovak = "Dauerauftrag" in German
- Subscription detection keywords differ by region
- Date/amount formats are locale-specific
We ended up with language-specific merchant dictionaries for common subscription services in each market.
What Actually Matters
The biggest lesson: people don't want a budgeting dashboard. They want a specific, actionable number.
"You're spending €137/month on forgotten subscriptions" converts. "Your spending breakdown by category" does not.
The product is live at vestelonflow.com — first report is free, no card required, no bank connection needed.
Happy to answer questions about the PDF parsing approach, the LLM pipeline, or the localization challenges.