BolBill: Voice-First PayPal Invoicing Agent

Speak a bill in Hindi or English and BolBill creates a real PayPal invoice, catches mistakes before money moves, and chases late payments. Built for small merchants billing customers abroad.

Comment

Inspiration

Millions of small shopkeepers and freelancers find invoicing software hard to use: forms, English-only menus, complicated dashboards. Many also bill customers abroad, where PayPal is the natural way to get paid. We wanted billing to be as easy as saying the amount out loud, in your own language.

What it does

BolBill is a voice-first invoicing agent built on PayPal.

  • Speak a bill in Hindi, English, Marathi, Tamil or Bengali: "Sharma ji ko 19 kilo chawal ka bill bhejo, 17 rupaye per kilo."
  • Gemini parses the speech into customer, items, prices, currency and due date.
  • Rupees to dollars: rupee amounts are converted with the latest ECB reference rate, shown on screen, and sent as a USD PayPal invoice.
  • Read-back and confirmation: the app reads the bill aloud and waits for a big green tick. Nothing is sent without it.
  • Safety checks before money moves: possible duplicates, amounts far above a customer's usual bill, very large bills, and a number cross-check that warns when the AI's reading of a number differs from what was actually said.
  • Real PayPal invoices: created and sent through the PayPal Invoicing API.
  • Live dashboard: Paid / Waiting / Late tiles read from PayPal, with earnings for today, the last 7 days and this month.
  • Ask your business by voice: "How much did I earn today?", "Who hasn't paid me?"
  • Agent actions with human approval: "Remind everyone who is late" drafts a polite reminder in each customer's language and sends it through PayPal after confirmation. "Sharma paid me" records a cash or UPI payment on the PayPal invoice.

How we built it

  • Backend: Node.js and Express
  • Frontend: mobile-first web app using the browser's Web Speech API for voice in and out
  • PayPal: Invoicing v2 API in the sandbox: create, send, list, remind and record payment
  • AI: Google Gemini (@google/genai) with JSON output at temperature 0, plus retries and a fallback model
  • Exchange rates: Frankfurter (ECB reference rates)
  • Hosting: Render

Arithmetic and currency conversion are done in code, not by the AI. The AI handles language, and code handles money.

Challenges

  • The AI once misread a spoken price (₹17 became ₹15), so we added a check that compares the numbers it extracted with the numbers in the transcript and warns the user.
  • PayPal blocks invoices to customers inside India, so we focused on merchants who bill international customers.
  • Gemini model overloads and a retired model name pushed us to add retries and automatic fallback.
  • Free hosting resets its disk, so the dashboard now reads invoices straight from PayPal.

Accomplishments we're proud of

A complete voice-to-PayPal-invoice loop that works end to end, with human confirmation on every action that moves money.

What we learned

Voice interfaces need confirmation and numeric validation when money is involved, and AI works best when it reasons about language while ordinary code does the math.

What's next

WhatsApp input and reminders, UPI and local payment methods, a real database, offline support, and more languages and currencies.

Note: BolBill runs on the PayPal sandbox. No real money moves.

Built With

Share this project:

Updates

Submission history