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

# SI On-Demand

> Trigger a sale against an existing Variable standing instruction mandate by Mandate ID.

## SI On-Demand Deduction

Execute a payment against an existing mandate whenever you need to charge the customer. Used for **VARIABLE** SI mandates with `ONDEMAND` frequency, where YOU control both timing AND amount.

<Note>
  Only works with **VARIABLE** SI mandates. For Fixed mandates with Auto Debit enabled, PayGlocal initiates the debit automatically — no on-demand call needed.
</Note>

***

## Endpoint

```
POST /gl/v1/payments/si/sale
```

***

## Request

```json theme={null}
{
  "merchantTxnId": "SALE-23AEE8CB6B62EE2AF07",
  "paymentData":   { "totalAmount": "89" },
  "standingInstruction": {
    "mandateId": "md_94f0bb40-2664-4851-ab83-b86c618d3e15"
  }
}
```

For **Fixed SI** mandates (where you're triggering a charge for the pre-set amount):

```json theme={null}
{
  "merchantTxnId": "SALE-23AEE8CB6B62EE2AF07",
  "standingInstruction": {
    "mandateId": "md_94f0bb40-2664-4851-ab83-b86c618d3e15"
  }
}
```

***

## When to Use

* Billing cycle arrived
* Service usage accumulated
* Customer requested a top-up
* Scheduled billing dates where you control timing

***

## Business Scenarios

Perfect for variable utility bills, usage-based charging, one-time top-ups within subscription plans, or scheduled billing dates where you control timing.

***

## Response

```json theme={null}
{
  "gid":       "gl-13bbd3c4-9817-4786-96c6-12fa6191f118",
  "status":    "SENT_FOR_CAPTURE",
  "message":   "Sent for Capture Successfully",
  "timestamp": "2026-04-12T07:47:18Z"
}
```

### Error Cases

```json theme={null}
{ "status": "REQUEST_ERROR", "message": "Mandate is not found | Mandate is inactive | Mandate is exhausted" }
```

<Warning>
  The API returns immediately with status. **Final payment confirmation comes via webhook** — always implement webhook handlers for production systems.
</Warning>

***

## Constraints

* For VARIABLE mandates: `totalAmount` must be ≤ `maxAmount` set during mandate creation.
* Each call requires a unique `merchantTxnId`.
* Mandate must be in `ACTIVE` status (not paused, revoked, or exhausted).