Invoice Hub — connect every provider of e-invoices
Integrate once with the Hub — issuance, digital signing and connecting to the tax authority for 1Invoice, MISA, Viettel, VNPT, FPT, M-Invoice. Use 1Invoice with free requests; other providers 50 VND per request. Bundled with payments in one end-to-end solution.
Instead of integrating separately with each invoice vendor, you connect once with Invoice Hub. The Hub routes to the right provider, issues and digitally signs invoices, and connects directly to the tax authority. A great fit for sales software, SaaS, PMS, HIS teams that want to save integration time.
Integrating each vendor separately — costs multiply
From the outside, all e-invoice providers do the same thing: create invoices, sign them, submit to the tax authority. But once you start integrating, each vendor is its own world — differing at almost every technical layer. When you (or your customers) use several vendors, the engineering team has to carry:
- !Writing and maintaining many separate integrations — each vendor with its own authentication (different API key, certificate, token), data structure and error reporting.
- !Handling differences in template codes, symbols, invoice number ranges and XML formats, each vendor with its own convention.
- !Learning each vendor's specific signing process: some use an HSM on the server, some a USB token, some sign on the vendor side — each a different integration flow.
- !Updating code every time a vendor changes its API or a regulation changes — and fixing it across all integrations at once.
- !Syncing invoice status yourself (issued / signed / submitted to the tax authority) from multiple sources with different notification mechanisms.
The big cost is not the first integration, but long-term maintenance: every vendor you add is another codebase to monitor, test and patch forever. With N providers, you are maintaining N integrations instead of one.
The one-API-many-providers model
Invoice Hub follows an adapter model: your software only talks to a single API contract from the Hub. Inside, the Hub keeps a converter (adapter) for each provider and routes requests to the right vendor.
A single invoice issuance through the Hub goes like this:
- 1Input standardization: you send invoice data in a unified Hub structure — no need to know which vendor is underneath.
- 2Routing: the Hub identifies the provider for that merchant/business case and hands off to the matching adapter.
- 3Translate to vendor format: the adapter maps standard data into XML and parameters exactly as the vendor requires, attaching the right template code/symbol/number range.
- 4Digital signing & tax submission: the Hub orchestrates signing and connects to the tax authority using each vendor's specific mechanism.
- 5Return standardized results: whichever provider is used, you receive a unified result structure (invoice code, status, lookup link).
Every difference between vendors is hidden behind one API layer. Your code does not change when the Hub adds a new vendor or when a vendor changes its API — the adapter changes, while your API contract stays the same.
Where do the vendors differ?
To see why one common API matters, look at exactly what differs between providers — the things you would have to handle yourself with a direct integration:
| Technical layer | Difference between vendors | Handled by the Hub |
|---|---|---|
| Template code / symbol / number range | Each vendor manages and allocates them by its own convention | Automatic mapping by configuration |
| Data format | XML structure, field names and data types differ | Translated from one standard structure |
| Authentication | API key, certificate, token — each vendor a different mechanism | You only hold one set of Hub keys |
| Digital signing | HSM on the server, USB token, or signing on the vendor side | Centrally orchestrated |
| Connecting to the tax authority | Separate submission and response flow per vendor | Standardized into one flow |
| Error & status reporting | Different error codes and notification styles | Mapped to one unified set of statuses |
If you do it yourself, each cell on the right is a separate body of work you must research, write and maintain for every vendor. The Hub folds it all into one API contract.
One API — every invoice provider covered
You call one standardized API set, the Hub routes each request to the correct provider, issues compliant invoices and returns the results. The full spec (create invoice, signing, fetch number ranges, lookup) is in the TCONNECT e-invoice API documentation.
| Criterion | Direct integration per vendor | Invoice Hub (TCONNECT × 1Invoice) |
|---|---|---|
| Number of integrations | One per vendor | Just one |
| API set | Many different sets | One standardized API set |
| Auth mechanisms to keep | Many keys/certificates | One set of Hub keys |
| Adding a new provider | Write a new integration | Enable it in the Hub |
| When a vendor changes its API | You must fix code | The Hub updates the adapter |
| Signing & tax submission | Handle per vendor | The Hub handles it centrally |
| Status sync | Stitch from many sources | Webhooks & standardized status |
| Bundled with payments | Integrate separately | Built in — one API solution |
Issue exactly once, reconcile status
Issuing invoices is a cannot-get-it-wrong operation: duplicate issuance or lost status both cause accounting and tax-authority headaches. The Hub is designed to be reliable to integrate with, not just convenient:
- ✓Duplicate protection (idempotency): each request can carry its own idempotency key, so if you accidentally resend over a flaky network, the Hub recognizes it and does not issue a second invoice.
- ✓Issuance-status webhooks: instead of constantly polling, your system receives proactive notifications when an invoice changes status.
- ✓Retry mechanism: when a vendor or the connection temporarily fails, the Hub retries safely without creating duplicates.
- ✓Status reconciliation: you can look up and reconcile which step an invoice is in — issued, signed, submitted to the tax authority — on one standardized set of statuses.
Building these mechanisms per vendor would be very costly and error-prone. Consolidating into one Hub means you write reconciliation logic once and use it for every underlying provider.
Free API requests when using 1Invoice
Invoice Hub is built on the 1Invoice platform — also the default provider, connected out of the box in the Hub. The request-fee policy is very simple:
| Invoice provider used through the Hub | Fee per API request |
|---|---|
| 1Invoice (default, pre-connected) | Free |
| Other providers (MISA, Viettel, VNPT, FPT, M-Invoice...) | 50 VND per request |
Issue invoices through 1Invoice and each API call incurs no request fee; only when you route to another provider does the Hub charge 50 VND per request. You still freely choose the underlying provider without rewriting the integration.
Suppose in a month you issue 100,000 invoices. If everything runs on 1Invoice, the request fee is 0. If for business reasons you route 10,000 invoices to another vendor, that portion costs 10,000 × 50 VND = 500,000 VND; the remaining 90,000 invoices on 1Invoice are still free. The cost-optimal approach is to keep 1Invoice as the default and route to another vendor only when truly needed.
When should you route to another vendor? When your customer already has a contract/invoice branding with a specific vendor, or when the business case requires keeping the current provider. For all other cases, using 1Invoice by default lets you eliminate request fees entirely while retaining the ability to switch vendors at any time.
What Invoice Hub does for you
- ✓Centralized connectivity: one API linking multiple invoice providers, with no separate coding for each.
- ✓Automation: automatically create, issue and send invoices the moment a transaction occurs.
- ✓Invoice digital signing: sign in line with current regulations before submitting to the tax authority.
- ✓Tax-authority connection: issued in line with current regulations, connecting directly to the tax authority.
- ✓Management & storage: look up, download PDF/XML, secure cloud storage.
Bundling payments + invoicing in one solution
This is the biggest differentiator versus a pure invoice gateway. With a standalone invoicing solution, the flow is usually: receive money in the payment system, then call the invoice system — two systems, two touchpoints, sync it yourself. With TCONNECT, payment and invoicing share one API solution.
- ✓Auto-issue on successful payment: right at the moment of the transaction, the invoice is issued — no manual step in between.
- ✓Auto-fill the buyer: buyer information is auto-filled via tax-code lookup before issuance, reducing manual entry and errors.
- ✓One touchpoint: one documentation set, one set of keys, one place for support — instead of stitching multiple providers.
The Hub standardizes the API so sales software, SaaS, PMS and HIS connect quickly; swap or add underlying providers without rewriting the integration.
Already using one vendor — how do you move to the Hub?
The biggest fear when changing infrastructure is having to rewrite. With Invoice Hub, you do not rewrite the integration every time you change providers: you connect once to the Hub's API contract, while choosing or switching the underlying vendor is a configuration action.
- ✓Keep your business logic: your invoice-creation code talks to the Hub, not tied to a specific vendor.
- ✓Migrate gradually: you can issue new invoices through the Hub while still looking up old data.
- ✓Flexible later: when you need to add another vendor for a customer group, you enable it in the Hub instead of opening a new integration project.
Applications by software type
With the same Hub, each industry taps into it for its own needs — but all benefit from connecting once:
| Software type | How to use Invoice Hub |
|---|---|
| Retail POS | Issue invoices right at the counter on payment, printed with a lookup QR. |
| F&B / restaurants | Issue when the guest pays the table, even across outlets using different providers. |
| SaaS billing | Auto-issue invoices per subscription cycle, reconcile status via webhook. |
| Hotel PMS | Auto-issue invoices at guest check-out, bundling services from the stay. |
| Hospital HIS | Issue hospital-fee invoices after visits/treatment, connecting to the tax authority in line with current regulations. |
| ERP / management software | One integration serving many customers using different invoice vendors. |
Friendly to developers and AI coding agents
Because the Hub provides one standardized API set instead of many different ones, the development team only has to learn one contract and one documentation set. This is also especially suited to AI coding agents: with a consistent API and clear docs, the machine generates integration code faster and with far fewer errors than stitching several different vendor specs.
- ✓A single documentation set: reading the e-invoice API documentation is enough to get started.
- ✓Standardized results: the same response structure regardless of the underlying vendor — easy to write handling logic.
- ✓Less maintenance surface: when a vendor changes its API, you do not have to fix anything — your code surface stays the same.
Connect Invoice Hub for your software
See the e-invoice integration API documentation, or contact us for advice on connecting to your specific business case.
TCONNECT is an infrastructure platform providing payment APIs (VietQR, payment gateway, POS, Soundbox) and e-invoices through a single integration, for PSPs, SaaS, ERP and businesses in Vietnam.