Cash Book : Expense Tracker — API integration & OpenData export

Deliverables checklist

• OpenAPI 3.1 specification covering auth, transactions, budgets, exports
• Protocol & auth flow report (token chain, local-DB schema, backup format)
• Runnable reference source in Python (FastAPI) and Node.js (Express)
• Postman collection plus pytest/Jest integration tests against a sandbox
• Compliance guidance covering GDPR, PSD2 AISP scope, and India's DPDP Act

Engagement options

• Source-code delivery from $300: we hand over the runnable repo and docs; you pay after delivery on satisfaction.
• Pay-per-call API: call our hosted endpoint and pay only for the requests you make — no upfront commitment.
• Custom retainer: ongoing maintenance when the app updates its data model, recurring reminder format, or backup file layout.

1. Family or household consolidation

A spouse or parent runs Cash Book : Expense Tracker on a personal phone while another family member tracks shared spending separately. We expose a per-user transaction endpoint and a budget-merge service so a shared web dashboard can pull both ledgers, deduplicate cross-payments, and present one household view. The integration uses our paginated /transactions read plus a server-side reconciliation step keyed on (date, amount, counterparty).

2. Small-business books → accounting stack

Indian SME-style cashbook usage is common — shop owners record till entries, supplier payments, and small expenses. We pipe these into Tally, Zoho Books, or QuickBooks Online via their respective ledger-entry APIs, mapping app categories to chart-of-accounts. The flow uses webhooks (entry created → push) plus a nightly reconciliation that re-reads our /exports endpoint and verifies totals.

3. Tax season export pack

An accountant needs a clean year-end pack: itemized expense list with categories, monthly summaries, and an audit-ready PDF. We orchestrate /exports?format=excel&range=fy2025 and /exports?format=pdf, attach a generated cover sheet, and drop the bundle into the user's preferred storage (S3, Drive, Dropbox). The mapping respects local tax categories, e.g. business-vs-personal split for Indian ITR or US Schedule C.

4. Dashboard / BI feed

A wealth coach or co-living operator wants a live BI feed of multiple users' spending categories (with consent) to spot saving opportunities. We provide an OpenData read replica with per-user partitioning and a Looker / Metabase connector. Each user's data is keyed to their consent token and can be revoked at any time, mirroring the AISP consent model from PSD2.

5. After-Call enrichment hook

The app's After-Call feature creates a quick income/expense entry right after a phone call ends. We surface this via a webhook so a CRM or collections tool can attach the entry to the matching contact, enrich it with caller context, and post an updated balance. Useful for field-sales, freelance, or kiranas that want a call → invoice → entry trail without manual reconciliation.

Authorization & session

POST /api/v1/cashbook/auth/token
Content-Type: application/json

{
  "grant_type": "user_consent",
  "device_id": "ANDROID_d4c7...",
  "consent_token": "eyJhbGciOi...",
  "scope": "transactions.read budgets.read exports.read"
}

200 OK
{
  "access_token": "eyJhbG...",
  "expires_in": 3600,
  "refresh_token": "rt_...",
  "scope_granted": ["transactions.read","budgets.read","exports.read"]
}

Transaction history (paged)

GET /api/v1/cashbook/transactions
  ?from=2026-04-01&to=2026-04-30
  &category=groceries,utilities
  &page=1&page_size=100
Authorization: Bearer <ACCESS_TOKEN>

200 OK
{
  "items": [
    {
      "id": "txn_018f5c...",
      "date": "2026-04-12",
      "amount": -42.50,
      "currency": "INR",
      "type": "expense",
      "category": "groceries",
      "note": "weekly produce",
      "source": "manual"
    }
  ],
  "page": 1,
  "page_size": 100,
  "total": 87
}

Statement export & webhook

POST /api/v1/cashbook/exports
{
  "format": "xlsx",
  "range": "month",
  "month": "2026-04",
  "include_categories": true,
  "include_notes": true
}

202 Accepted
{ "export_id": "exp_91c...", "status": "queued" }

# Later, via webhook:
POST https://your-callback/cashbook/export-ready
{
  "export_id": "exp_91c...",
  "status": "ready",
  "download_url": "https://exports.openfinance-lab.com/exp_91c...xlsx",
  "expires_at": "2026-05-04T12:00:00Z"
}

Regulatory alignment

Personal-finance ledger data is sensitive even when self-entered, so every integration is shipped with a privacy review. For EU users we follow GDPR (lawful basis: explicit consent), apply data minimization, and document retention windows per data type. Where a deployment surfaces banking-adjacent flows, we map our consent and access-control patterns to PSD2's AISP model — useful when a budgeting product later wants to enrich Cash Book data with bank-account aggregation. For Indian users we align with the Digital Personal Data Protection Act (DPDP, 2023) for purpose-limitation and breach-notification.

Operational controls

• Per-user consent token, revocable at any time, with audit log
• Field-level encryption for note bodies and category metadata at rest
• Scope-limited tokens (read-only by default; export scope opt-in)
• Automated PII redaction on logs and exception traces
• Optional in-region hosting (EU, IN, US, SG) for residency requirements

Money Manager

Manual-entry mobile ledger with strong visualization. Holds account-level transactions and categories — users who switch from Money Manager often need a one-time ledger migration plus an ongoing category-mapping layer.

YNAB (You Need A Budget)

Zero-based budgeting platform with a public API. Teams that combine YNAB with a manual cashbook need a unifier that aligns YNAB's "categories" with Cash Book's category tree.

Mint (Intuit)

Bank-aggregator-driven budgeting; held the largest US footprint historically. AI-driven insights in 2025 raised user expectations for category and trend exports — useful context when scoping an OpenData layer on Cash Book.

PocketGuard

Cash-flow-first budgeting around an "In My Pocket" number. Surface area is similar to Cash Book's budget vs actual delta, so a shared variance API can drive both.

Wallet by BudgetBakers

Cross-device cloud-sync expense tracker. Often paired with manual cashbooks for cash-only flows; a unified transaction feed is the most common request.

Expensify

Receipt-and-report-centric, with a documented integration API. Useful when an SME wants to push Cash Book entries into reimbursable expense reports.

Simplifi by Quicken

Subscription budgeting tool with monthly spending plans. Customers running Simplifi for forecasts plus Cash Book for cash entries want a merged monthly view.

Monarch Money

Household-finance dashboard with shared budgets. Typical use case: pull Cash Book entries into Monarch's shared category structure for couples.

EveryDollar

Zero-based budgeting around the Ramsey method. Teams using EveryDollar for plans plus Cash Book for execution benefit from a daily delta sync.

Cashbook (Digital Khata)

Indian small-business cashbook with UPI receipts and Tally / Zoho push. Common adjacent app for shop owners who additionally use Cash Book : Expense Tracker for personal entries.

About us

OpenFinance Lab is an independent studio focused on app protocol analysis, OpenData, and OpenFinance integration. Engineers on the team come from retail banks, payment processors, mobile reverse-engineering teams, and cloud platforms. We have shipped end-to-end financial APIs for fintech, e-commerce, travel, and personal-finance categories, and we know what it takes to keep them compliant under GDPR, PSD2, India's DPDP Act, and similar regimes.

• Personal finance, payments, digital banking, and cross-border clearing
• Mobile protocol analysis on Android (Java/Kotlin, native) and iOS
• Custom Python / Node.js / Go / Kotlin / Swift SDKs and test harnesses
• Source-code delivery from $300, paid after delivery on satisfaction
• Pay-per-call hosted API with no upfront cost — usage-based pricing

Contact

Send us the target app and your concrete needs (data types, scopes, regions, deadline). We reply with a short scoping note, a price, and a delivery window.

Contact page

Engagement workflow

1. Scope confirmation: target endpoints (transactions, budgets, exports, backup mirror), regions, compliance posture.
2. Protocol analysis & API design (2–5 business days).
3. Implementation and internal validation against a sandbox install (3–8 business days).
4. Documentation, samples, and Postman / pytest test cases (1–2 business days).
5. Handover. First delivery typically 5–15 business days; downstream accounting-stack push may extend the schedule.

FAQ

What data can be extracted from Cash Book : Expense Tracker?

How long does the integration delivery take?

Is the integration compliant with GDPR and other privacy regulations?

Do you support both Android and iOS clients?