Reading the loan ledger and repayment plan inside Ví Tốt

A Ví Tốt account carries a single revolving credit line — 500,000 to 100,000,000 VND according to its Play Store listing — and on top of it the installment plan the app builds for each borrower. Terms run 90 to 365 days, split into 3 to 12 periods, with the annual rate held at or under 36% as required by Vietnamese law. None of that is a static document. The available limit moves as the borrower draws and repays, the schedule recomputes per period, and a credit-decision tier sits behind it deciding the offered amount and rate. That is the data a servicing tool, a BNPL aggregator, or an underwriting model actually wants, and it only exists inside the borrower's authenticated session.

OpenBanking Studio builds the authorized path to that session and hands you runnable code that reads it. You bring the app name — Ví Tốt, package com.northasiatech.vitot per the store listing — and what you need out of it. We work out the route, the auth chain, and the field shapes, then deliver source plus documentation.

What sits behind a Ví Tốt login

Each row below is a real surface the app presents to its user, named the way Ví Tốt names it where the description gives a label. The granularity is what an integrator can expect to read once a consented session is in place.

Authorized routes to the data

Three routes apply to Ví Tốt, and they reach different things. We set up whichever is needed during onboarding — a consenting test account, the credentials, and the compliance paperwork are arranged with you as part of the project, not asked for up front.

Borrower-consented interface integration

With the borrower's authorization we map the app's own login-to-data traffic: the device-bound sign-in, the token it returns, and the JSON behind the credit-line, schedule and history screens. This reaches everything the borrower can see. Effort is moderate; durability is tied to the app version, so the parser tracks releases.

User-linked session access

The borrower links their own login and we ride the access/refresh token under that consent. Same per-user scope as above, but a cleaner consent trail that follows the PDP Law lifecycle — useful when the end user, not a test account, is the data owner.

Consent-based open-banking rails

SBV Circular 64/2024/TT-NHNN defines AIS calls — Get Account List, Get Account Information, Get Transaction History — behind an OAuth 2.0 consent. Those describe a bank account, so they fit the disbursement-bank side of a loan rather than Ví Tốt's amortization plan. We keep them in view because the regime phases in toward full compliance on March 1, 2027.

For Ví Tốt specifically, the consented interface route is the one worth building first. It is the only path that returns the installment schedule and the credit-line state; the open-banking account APIs never carry a lender's repayment plan, only the bank balance underneath a disbursement. The regulated rails stay a complement for the funding-bank leg, not a substitute for reading the loan itself.

The schedule call, sketched

Illustrative shapes from the build — paths and field names are confirmed against a consenting account during the engagement, not published here. The point is the chain: device-bound login, a short-lived token, then the line and the per-period schedule.

# 1) device-bound login -> access + refresh token
POST /api/v1/auth/token
  { "device_id": "...", "phone": "0xxxxxxxxx", "otp": "######" }
  -> { "access_token": "...", "refresh_token": "...", "expires_in": 1800 }

# 2) credit line snapshot
GET /api/v1/credit/line          Authorization: Bearer <access_token>
  -> { "limit": 100000000, "used": 50000000, "available": 50000000,
       "currency": "VND", "apr_tier": 0.18 }

# 3) installment schedule for an active loan
GET /api/v1/loans/{loan_id}/schedule
  -> { "loan_id": "...", "principal": 50000000, "term_periods": 12,
       "apr": 0.18,                      # bounded by 0.36 under VN law
       "schedule": [
         { "period": 1, "due_date": "2026-07-25",
           "principal_due": 4166667, "interest_due": 750000,
           "status": "due" } ] }

# token expiry -> 401; refresh once, then re-issue the read. Back off on 429.

The worked example in the app's own description — 50,000,000 VND over 12 periods at 18% giving roughly 4,916,667 VND a month — is the reconciliation target. Our normalizer reproduces that rounding so the reconstructed schedule matches the displayed figures, period by period.

What lands in your repo

Every artifact is tied to the surfaces above, not a generic kit:

• An OpenAPI/Swagger spec covering the token, credit-line, schedule and repayment-history calls, with VND units and APR encoding documented per field.
• A protocol and auth-flow report: the device-bound login, the OTP step, and the access/refresh token chain as Ví Tốt implements it.
• Runnable source in Python and Node.js for those endpoints, including refresh-on-401 handling and rate-limit back-off.
• Automated tests that run against a consenting account or recorded fixtures, asserting the schedule reconciles to the app's displayed totals.
• Interface documentation an in-house team can maintain, plus retention and consent-record guidance aligned to the PDP Law.

Consent rules for credit data in Vietnam

Two instruments shape this work. Vietnam's Law on Personal Data Protection, passed 26 June 2025 and in force since 1 January 2026, replaces Decree 13/2023 and keeps consent voluntary, explicit, purpose-specific and easily revoked; its Article 27 on banking and finance specifically bars using credit information for scoring without consent. So every pull is scoped to a stated purpose, logged, and stops when consent is withdrawn. Separately, Decree 94/2025/ND-CP opened an SBV-supervised sandbox from 1 July 2025 covering peer-to-peer lending, credit scoring and Open API data sharing — the regulatory space this category of app operates in. We work authorized, documented, data-minimized, and under NDA where a project needs it, and we keep consent and access records that match what these rules expect.

What we plan the build around

Two things about Ví Tốt shape the engineering, and we handle both:

• Schedule math has to be exact. The app computes per-period principal and interest under a 36% APR ceiling and rounds the way its example shows. We mirror that arithmetic so our reconstructed figures match to the dong, rather than drifting by a few hundred VND a period and breaking reconciliation.
• Consent has a lifecycle, not a switch. Under the PDP Law a borrower can revoke at any time. We design the sync so a revoked consent halts the pull and triggers purge on the agreed retention window, instead of quietly continuing against a stale grant.
• Android-first and frequently updated. The app ships installment-feature changes often, so we keep a version watch and refresh the parser when the repayment-plan screen changes shape, before the data feed degrades.

Where this data gets used

• A loan-servicing platform reading each borrower's next due date and amount to schedule reminders and reconcile repayments.
• A BNPL aggregator normalizing Ví Tốt's 3-to-12-period schedule alongside other lenders into one repayment calendar per user.
• An accounting tool matching disbursement and repayment events into a ledger for a portfolio of borrowers.
• A credit marketplace checking the decision tier before routing a user to one offer or another.

Cost and how the build runs

Source delivery starts at $300, and you pay only after the code is in your hands and runs against a consenting Ví Tốt account. That package is the runnable endpoints, the spec, the auth-flow report, the tests and the documentation, on a one-to-two-week cycle. If you would rather not host anything, the second model is a pay-per-call hosted API: we run the integration, you call our endpoints and pay per call, with no upfront fee. Either way the studio handles the route, the protocol work and the maintenance. Tell us what you want out of Ví Tốt and we will scope it — start a project here.

Screens we mapped against

The Play Store screenshots used while sketching the surfaces above. Open any to enlarge.

How this brief was built

Checked on 25 June 2026: the Ví Tốt Play Store listing for the loan terms, operator and platform; the State Bank of Vietnam press release and the English text of Circular 64/2024/TT-NHNN for the Open API and AIS calls; a legal summary of Vietnam's new Personal Data Protection Law for the consent regime; and a firm note on Decree 94/2025 for the fintech sandbox. Figures cited as the app's own come from its store description and are reconciled, not assumed.

• Ví Tốt on Google Play (com.northasiatech.vitot)
• SBV press release on Circular 64/2024/TT-NHNN
• Circular 64/2024/TT-NHNN, English text
• Vietnam's Personal Data Protection Law summary

Researched and written at the OpenBanking Studio integration desk, June 2026.

Other Vietnamese lenders in the same orbit

Same category, useful when several lenders feed one consolidated view. Listed for context, not ranked.

• MoMo — a large wallet with a lending arm; holds linked-account, loan and repayment records across a wide user base.
• Home Credit — point-of-sale and cash consumer loans with installment plans and disbursement records.
• FE Credit — licensed consumer-finance lender with card and cash-loan accounts and amortization schedules.
• Tima — a lending-connection platform matching borrowers with licensed lenders and investors, holding application and matching data.
• Doctor Đồng — short-term online loans with per-loan status and repayment timelines.
• Cake by VPBank — a digital bank with deposit, card and credit-line balances behind a single login.
• Viettel Money — a mobile-money service carrying wallet balances, transfers and consumer-credit links.
• SHB Finance — consumer-finance loans and installment accounts under a licensed lender.

Questions integrators ask about Ví Tốt

Can you separate Ví Tốt's installment schedule from the credit-line balance?

Yes. The repayment plan (Kế hoạch trả nợ) and the available limit (Hạn mức vay) are distinct surfaces in the app, so we model them as separate resources: one schedule object with per-period principal, interest and due date, and one credit-line object with limit, used and available amounts in VND.

Does Vietnam's Open API circular cover a lender like Ví Tốt directly?

Circular 64/2024/TT-NHNN binds banks, not a standalone consumer lender. For a Ví Tốt borrower's own loan data the working route is the consent-based interface to the app itself, while the regulated AIS rails are relevant on the disbursement-bank side as they phase in toward the March 1, 2027 compliance date.

How do you keep the reconstructed schedule matching what the borrower sees in Ví Tốt?

We mirror the app's own math: the APR ceiling of 36% per Vietnamese law and the per-period rounding shown in its worked example, where 50,000,000 VND over 12 periods rounds to about 4,166,667 VND of principal a period. Reconstructed figures are reconciled to the app's displayed amounts to the dong.

If Ví Tốt ships an Android update mid-build, does the integration break?

We keep a version watch on the app, which is Android-first and updates its installment features often. When the repayment-plan screen changes shape the parser is updated before the data goes stale, and the build still lands inside the one-to-two-week cycle.