Payments - Introduction / Learning brief
Brazil's Pix and STR
Your notes
In simple terms / 01
What this means in plain language
Brazil's Pix settles instant retail payments individually over the central bank's SPI, addressed by a simple Pix key, while the STR moves high-value interbank obligations gross in central-bank reserves — the retail-instant and wholesale-RTGS halves of the Banco Central do Brasil's system.
Complete lesson / 02
Understand the full idea, step by step
A market stall in São Paulo, a phone held up, a short beep — and before the seller has counted out any change, the money is already on their account, final. It is a Sunday evening; no bank branch is open, no card network sits in the middle. Behind that everyday scene are two very different Brazilian rails built and run by the same central bank: one for instant retail payments like this one, and one for the far larger interbank transfers that never touch a shopper's phone. Telling the two apart is what this lesson is for.
Pix at a glance
- What it is
- Brazil's instant retail payment platform
- Run by
- Banco Central do Brasil (BCB)
- Settles over
- SPI — the Instant Payment System, an RTGS in central bank money
- Addressing
- Pix key resolved through the DICT directory (no account number shared)
- Availability
- 24 hours a day, every day
- Finality
- Final and irrevocable within seconds
Two halves of one central bank's plumbing
It helps to see the Banco Central do Brasil running two rails side by side. Pix is the retail half: an instant payment platform for people and businesses, settling small and medium payments around the clock. Each Pix settles individually over the SPI (Sistema de Pagamentos Instantâneos, the Instant Payment System) — an instant real-time gross settlement rail — in central bank money, one payment at a time, final and irrevocable. The other half is the STR, the wholesale rail: the reserve-transfer RTGS that moves high-value interbank obligations across the banks' reserve accounts during business hours. Same central bank, same gross-settlement idea; very different jobs. Pix is the shopper's rail; the STR is the banks' rail.
Pix — the Banco Central do Brasil's instant retail payment platform
Pix is the instant payment platform created and operated by the Banco Central do Brasil. A customer starts a payment from their own bank app; the payment settles individually over the SPI in central bank money and is final within seconds, at any hour of any day. Two things make it feel different from an older transfer: it is always on, and it is addressed by a Pix key rather than by account and branch numbers. What settles is not a promise between banks to reconcile later — it is a completed transfer in central bank money that cannot be pulled back.
Proxy addressing (the Pix key and DICT) — paying to a simple alias that a directory resolves to the real account
A Pix key is a proxy: a phone number, an email address, a tax ID, or a random string that stands in for the payee's account. When Riya pays, Bank Alfa asks the DICT directory (the Transactional Account Identifier Directory) which account the key points to, and DICT answers with Arjun's account at Nordbank. Riya never sees or shares an account number. The directory does the addressing; the SPI does the settling. Getting the account right happens before any money moves — if the key does not resolve, the payment stops before a debit is ever booked.
You may be wondering: if a Pix is final in seconds, when exactly does the money actually move — at the beep, or before?
The beep on Arjun's phone comes after the money has moved, not before. In order, Bank Alfa first commits the debit on Riya's account, then the SPI settles the one transfer across the two banks' accounts at the Banco Central do Brasil, in central bank money. Only once that settlement is final does Nordbank book the credit and let Arjun spend it. The whole sequence takes a few seconds, which is why it feels instant — but the finality is real settlement in central bank money, not a display trick.
A Pix payment, step by step
- INSTRUCTION
Riya types Arjun's phone number as his Pix key and asks Bank Alfa to pay BRL 150.00. She never has to know his account number.
- VALIDATION
Bank Alfa asks the DICT directory which account the key points to; DICT answers with Arjun's account at Nordbank. Addressing is settled before money moves.
- LEDGER
Bank Alfa books the debit on Riya's account, committing the funds before submitting the payment to the central bank's system.
- SETTLEMENT
The SPI settles this one transfer individually, in central bank money, across Bank Alfa's and Nordbank's accounts at the BCB — final and irrevocable.
- NOTIFICATION
Nordbank credits Arjun and notifies him; the money is his to spend immediately, at any hour.
Read the steps as text
- 01MessageRiya enters Arjun's Pix keyRiya (payer) → Bank Alfa (payer PSP)
Riya types Arjun's phone number as his Pix key and never has to know or share his account number. Pix works 24 hours a day, every day, with no fee to send.
- 02MessageThe DICT directory resolves the Pix keyBank Alfa (payer PSP) → Pix / DICT directory
Bank Alfa asks the DICT directory (the Transaction Accounts Identifier Directory) which account a Pix key points to. DICT answers with Arjun's account at Nordbank.
- 03PostingBank Alfa debits RiyaBank Alfa (payer PSP)
Bank Alfa books the debit on Riya's account on its own ledger, so the funds are committed before the payment is submitted to the central bank's system.
- DR Riya's account at Bank Alfa — BRL 150.00
- 04SettlementThe SPI settles the payment in central bank moneyBank Alfa (payer PSP) → Nordbank (payee PSP)
The payment is submitted to the SPI (Instant Payment System), an RTGS operated by the BCB. It settles this one transfer individually, one-to-one, in central bank money — final and irrevocable, in about three seconds on average.
- DR Bank Alfa settlement account at the BCB — BRL 150.00
- CR Nordbank settlement account at the BCB — BRL 150.00
- 05PostingNordbank credits ArjunNordbank (payee PSP)
Once settlement is final, Nordbank books the credit to Arjun's account. He can spend the money immediately, at any time of day.
- CR Arjun's account at Nordbank — BRL 150.00
| Account | Dr | Cr |
|---|---|---|
| Bank Alfa settlement account at the BCB | BRL 150.00 | |
| Nordbank settlement account at the BCB | BRL 150.00 |
The customer-facing debit on Riya's account and credit to Arjun's are booked on each bank's own ledger; shown here is only the interbank leg that the SPI settles in central bank money.
The wholesale half: the STR
Now the other rail. The STR (Sistema de Transferência de Reservas, the Reserve Transfer System) is the Banco Central do Brasil's wholesale RTGS. It moves high-value interbank obligations one at a time, gross, across the banks' reserve accounts at the central bank — no netting, no waiting for a cycle. When Bank Alfa owes Nordbank BRL 3,000,000.00, the STR message asks the BCB to move it; the BCB checks Bank Alfa's reserve account actually holds the funds, then debits Bank Alfa and credits Nordbank in central-bank reserves, with immediate finality. An RTGS rail will not create reserves a bank does not have: if the account is short, the transfer is queued or held, and Bank Alfa must source liquidity in the interbank market. Unlike the always-on SPI, the STR runs in business hours.
RTGS — real-time gross settlement
In real-time gross settlement, each accepted payment settles on its own, in real time, for its full amount — no batching offsetting debits and credits into a single net figure. Both of Brazil's rails are RTGS in central bank money: the SPI settles retail Pix payments individually and around the clock, while the STR settles high-value interbank transfers individually in reserves during business hours. The trade-off is liquidity: because every payment settles gross, the sending bank must have the full amount available at the moment of settlement, which is why the STR queues a transfer a reserve account cannot yet cover.
Read the steps as text
- 01MessageBank Alfa submits the STR transferBank Alfa (sending bank) → STR (Reserve Transfer System)
The sending bank submits a Reserve Transfer System message to move a high-value interbank obligation to Nordbank. Nothing has moved yet — it is a request, not the money.
- 02MessageSTR checks Bank Alfa's reserve balanceSTR (Reserve Transfer System) → Banco Central do Brasil
The STR asks the Banco Central do Brasil whether Bank Alfa's reserve account holds the funds now — an RTGS rail will not create reserves a bank does not have.
- 03SettlementThe BCB settles the payment in central-bank reservesBank Alfa (sending bank) → Nordbank (receiving bank)
The Banco Central do Brasil debits Bank Alfa's reserve account and credits Nordbank's, one payment at a time, in central-bank reserves. Settlement is individual, gross, and final — it cannot be reversed.
- DR Bank Alfa's reserve account at the BCB — BRL 3,000,000.00
- CR Nordbank's reserve account at the BCB — BRL 3,000,000.00
- 04MessageNordbank is confirmed of the settled paymentSTR (Reserve Transfer System) → Nordbank (receiving bank)
The STR tells the receiving bank the reals are on its reserve account at the BCB and final, with the details it needs to book the funds.
- 05PostingNordbank books the fundsNordbank (receiving bank)
Because the interbank leg already settled with finality in central-bank reserves, Nordbank can book the credit on its own ledger without waiting for anything else.
- CR Interbank funds received at Nordbank — BRL 3,000,000.00
COMMON CONFUSION
“Because Pix is instant and free to the sender, there is no real settlement behind it — the banks just update a shared tally and square up later.”
Every Pix settles individually over the SPI in central bank money, and that settlement is final before Arjun is credited. Nothing is deferred and netted later; the SPI is an RTGS, so each payment settles gross on its own. "Instant" describes the speed, not the absence of settlement — the money genuinely moves across the banks' accounts at the Banco Central do Brasil within seconds.
STRICTLY SPEAKING
Strictly speaking, the SPI and the STR are distinct systems with different jobs, hours, and participants, even though the Banco Central do Brasil runs both. The durable lesson is the split: retail-instant settlement over the SPI (24/7, addressed by Pix keys through DICT) on one side, and wholesale reserve-transfer RTGS over the STR (business hours, high-value, gross in reserves) on the other. Operating hours, key types, limits, and the exact message steps are arrangements that have changed over time and can change again.
FOR NOW, REMEMBER
- Pix is the Banco Central do Brasil's instant retail payment platform; each payment settles individually over the SPI (an instant RTGS) in central bank money, final and irrevocable, around the clock.
- A Pix key is a proxy address — a phone, email, tax ID, or random string — that the DICT directory resolves to the payee's account, so no account number is shared.
- The STR is the wholesale reserve-transfer RTGS: it moves high-value interbank obligations gross across the banks' reserve accounts at the BCB, during business hours.
- Both rails settle gross in central bank money; the split is retail-instant (Pix/SPI) versus wholesale (STR), not netting versus gross.
TRY IT YOURSELF
Asha Traders needs to move BRL 3,000,000.00 to another bank as a same-day interbank obligation, and separately its owner wants to pay a supplier BRL 150.00 on a Sunday night. Which rails fit, and why?
Brazil runs an instant retail rail and a wholesale RTGS as two halves of one central bank's plumbing. Step back and you can see the same shape in national payment systems the world over — and why countries keep drawing the line where they do.
KEEP GOINGKey takeaways / 03
Three things to remember
- 01
Identify who instructs, processes, clears, settles, and ultimately receives the funds.
- 02
Keep the exchange of payment information separate from the movement of money.
- 03
Trace where validation, accounting, charges, and exceptions enter the journey.
Operational sequence / 06
Follow the message and decision path
This compact sequence is a learning model. Exact routing and rulebook behavior can vary by scheme, participant, and implementation.
Read the steps as text
- 01MessageRiya enters Arjun's Pix keyRiya (payer) → Bank Alfa (payer PSP)
Riya types Arjun's phone number as his Pix key and never has to know or share his account number. Pix works 24 hours a day, every day, with no fee to send.
- 02MessageThe DICT directory resolves the Pix keyBank Alfa (payer PSP) → Pix / DICT directory
Bank Alfa asks the DICT directory (the Transaction Accounts Identifier Directory) which account a Pix key points to. DICT answers with Arjun's account at Nordbank.
- 03PostingBank Alfa debits RiyaBank Alfa (payer PSP)
Bank Alfa books the debit on Riya's account on its own ledger, so the funds are committed before the payment is submitted to the central bank's system.
- DR Riya's account at Bank Alfa — BRL 150.00
- 04SettlementThe SPI settles the payment in central bank moneyBank Alfa (payer PSP) → Nordbank (payee PSP)
The payment is submitted to the SPI (Instant Payment System), an RTGS operated by the BCB. It settles this one transfer individually, one-to-one, in central bank money — final and irrevocable, in about three seconds on average.
- DR Bank Alfa settlement account at the BCB — BRL 150.00
- CR Nordbank settlement account at the BCB — BRL 150.00
- 05PostingNordbank credits ArjunNordbank (payee PSP)
Once settlement is final, Nordbank books the credit to Arjun's account. He can spend the money immediately, at any time of day.
- CR Arjun's account at Nordbank — BRL 150.00
Read the steps as text
- 01MessageBank Alfa submits the STR transferBank Alfa (sending bank) → STR (Reserve Transfer System)
The sending bank submits a Reserve Transfer System message to move a high-value interbank obligation to Nordbank. Nothing has moved yet — it is a request, not the money.
- 02MessageSTR checks Bank Alfa's reserve balanceSTR (Reserve Transfer System) → Banco Central do Brasil
The STR asks the Banco Central do Brasil whether Bank Alfa's reserve account holds the funds now — an RTGS rail will not create reserves a bank does not have.
- 03SettlementThe BCB settles the payment in central-bank reservesBank Alfa (sending bank) → Nordbank (receiving bank)
The Banco Central do Brasil debits Bank Alfa's reserve account and credits Nordbank's, one payment at a time, in central-bank reserves. Settlement is individual, gross, and final — it cannot be reversed.
- DR Bank Alfa's reserve account at the BCB — BRL 3,000,000.00
- CR Nordbank's reserve account at the BCB — BRL 3,000,000.00
- 04MessageNordbank is confirmed of the settled paymentSTR (Reserve Transfer System) → Nordbank (receiving bank)
The STR tells the receiving bank the reals are on its reserve account at the BCB and final, with the details it needs to book the funds.
- 05PostingNordbank books the fundsNordbank (receiving bank)
Because the interbank leg already settled with finality in central-bank reserves, Nordbank can book the credit on its own ledger without waiting for anything else.
- CR Interbank funds received at Nordbank — BRL 3,000,000.00
Evidence & review / 07
Evidence & review
Pix, the SPI and the STR, Brazil (Banco Central do Brasil operated); the instant-retail-plus-wholesale-RTGS pattern generalises to other markets.
What this brief simplifies: The Pix DICT directory lookup and SPI settlement mechanics are compressed into one flow; STR operating hours are described qualitatively.
Sources for this brief2
- Official requirement
Pix, the Instant Payment System (SPI) and the Reserve Transfer System (STR) ↗ — Banco Central do Brasil · Pix settled over the SPI (instant RTGS) via DICT keys; STR wholesale reserve RTGS
Pix settles over the SPI (RTGS) in about three seconds; the STR is the wholesale reserve-transfer RTGS operated by the BCB.
- Simplified educational illustration
Payments Signal editorial teaching models — Payments Signal
Used wherever diagrams, scenarios, figures, or example values are didactic constructions rather than sourced facts; every such use carries a simplifications disclosure. All people, companies, banks, and list entries in examples are fictional.