> ## Documentation Index
> Fetch the complete documentation index at: https://docs.lerian.studio/llms.txt
> Use this file to discover all available pages before exploring further.

# What is Lerian SPB?

> Lerian's direct, non-intermediated BACEN STR connector for interbank and large-value transfers and reserve-account operations.

**Lerian SPB** is Lerian's own, non-intermediated messaging connector to the **STR** (Sistema de Transferência de Reservas), the real-time gross-settlement core of the Brazilian payment system. It reaches the STR over the **RSFN**, the private national network that carries payment-system messages between participants and the Central Bank of Brazil (BACEN).

It gives a participant institution a direct path to send and settle interbank and large-value wire transfers — the TED family — and reserve-account operations against BACEN's settlement system, with no connectivity partner between the institution and BACEN.

## Who it serves

***

Lerian SPB serves financial institutions that hold their own reserve and settlement account at BACEN. Those institutions send TED-family transfers, move liquidity between their reserve account and their liquidity account (Conta PI), and query their reserve position directly through the STR.

## An operation-centric API

***

You do not hand-pick a wire code. You declare the typed roles of the parties to an operation — who debits, who credits, and whether each side is an account-holding institution or a client — and the platform derives the correct STR message code for you.

| Declared parties           | STR code | Movement                                                      |
| -------------------------- | -------- | ------------------------------------------------------------- |
| Institution to institution | STR0004  | Interbank transfer between two account-holding participants   |
| Non-account-holders        | STR0005  | Transfer involving parties that do not hold a reserve account |
| Client to institution      | STR0006  | A client sends to an institution                              |
| Institution to client      | STR0007  | An institution sends to a client                              |
| Client to client           | STR0008  | Transfer between two clients across institutions              |

## Settlement is asynchronous

***

The STR is a real-time gross-settlement system: every operation settles individually against reserve balances. When you submit a transfer, the platform returns `SUBMITTED` — dispatch was accepted, **not** that BACEN has settled it. BACEN confirms asynchronously through a settlement reply (the R-leg), which moves the operation to `SETTLED` or `REJECTED` and carries BACEN's settlement fields (for example `numCtrlSTR` and `sitLancSTR`), projected verbatim.

## Money-neutrality

***

Lerian SPB is money-neutral by design. It forwards the amounts you declare exactly as declared and computes **no** balance or position of its own. Every accounting position lives in **Midaz**, the ledger; Lerian SPB carries the message, Midaz carries the money.

## Glossary

***

| Term                                           | Meaning                                                                                                          |
| ---------------------------------------------- | ---------------------------------------------------------------------------------------------------------------- |
| **STR** — Sistema de Transferência de Reservas | BACEN's real-time gross-settlement (RTGS) system, where each operation settles individually.                     |
| **SPB** — Sistema de Pagamentos Brasileiro     | The Brazilian payment system that the STR is the settlement core of.                                             |
| **RSFN**                                       | The private national financial-system network that carries SPB messages between participants and BACEN.          |
| **TED**                                        | An electronic wire transfer settled through the STR.                                                             |
| **NUOp**                                       | 23-digit BACEN operation identifier (ISPB + date + sequence) that correlates a submitted message with its reply. |
| **ISPB**                                       | 8-digit BACEN code identifying a payment-system participant institution.                                         |
| **Conta PI / reserve-settlement account**      | The accounts an institution holds at BACEN for settlement and liquidity.                                         |
| **ICP-Brasil certificate**                     | The digital certificate used to sign outbound SPB messages.                                                      |
| **Settlement confirmation (R-leg)**            | The asynchronous BACEN reply that moves a submitted operation to `SETTLED` or `REJECTED`.                        |
| **STR / LPI / GEN codes**                      | Official BACEN protocol identifiers for each STR and SPB message type (for example STR0004, LPI0001, GEN0006).   |

For how Lerian SPB sits alongside the other native rails and the provider interfaces, see [Native Messaging](/en/rails/native/native-messaging).