The short answer: a payment confirmation SMS goes out once your system treats the payment as confirmed, never earlier. It says how much came in, what it was for (the invoice, the order, the instalment) and what happens next. You send it through the API, one request per payment, or by hand from the SMS Center in My MozOut. Customers stop calling to ask whether their money arrived.
When to send it
The right moment is when the payment is recorded in your system. A few cases:
| How the customer paid |
When the SMS goes out |
| At the counter or till |
When the cashier records the payment. |
| Mobile payment or payment reference |
When the payment service confirmation reaches your system. |
| Bank transfer |
When someone on your team checks the transfer and marks it as paid. |
| Part of the amount |
When the part payment is recorded, with the amount still due. |
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Do not confirm just because the customer came back from the payment page. Coming back is not proof of payment: the real confirmation arrives later, from the payment service. The reason is in synchronous or asynchronous.
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What to write
A good SMS receipt fits in one part and answers three questions: paid for what, how much, and what now? Examples:
| Case |
Message |
| Invoice paid |
We have received your payment of 1,500 USD for invoice FT 2026/118. Thank you. |
| Order paid |
Payment received. Order no. 3381 is now being prepared. |
| Instalment |
We received 2,000 USD for your November instalment. 6,000 USD left to pay. |
In Portuguese, leave out letters such as «ã» or «ç» where you can: one of them moves the whole message to the 70-character limit per part. See writing transactional SMS.
Through the API, without sending twice
| 1 |
The payment is confirmed in your system.
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| 2 |
Your system calls POST /v1/sms/messages with the number and the text, plus an Idempotency-Key header built from the payment number, such as payment-3381.
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| 3 |
It stores the returned id with the payment, so it can check the SMS status later.
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| 4 |
If the answer is a 422 error, it fixes whatever details.reason points to. The payment stays valid: the SMS is a consequence, never a condition.
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Did the payment service notify you twice? With the same Idempotency-Key and the same text, the API returns the first answer and the SMS does not go out again. More on the technique in retries and idempotency.
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Want every payment to confirm itself to the customer? See how Transactional SMS works.
See Transactional SMS
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