---
title: "Create a Rule"
url: https://docs.catalyst.zoho.com/en/tutorials/invoice-notifier/python/create-rule/
description: "Create an Event Driven Architecture to automate invoice updates from Zoho Books to Zoho Cliq using Event Functions and Catalyst Signals."
last_updated: 2026-08-17T12:16:04Z
service: All Services
type: tutorial
related_links:
  - name: "Publishers"
    url: /en/signals/help/publishers/key-aspects/
  - name: "Targets"
    url: /en/signals/help/targets/key-aspects/
  - name: "Rules"
    url: /en/signals/help/rules/key-aspects/
  - name: "Events"
    url: /en/signals/help/events/key-aspects/
  - name: "Event Functions"
    url: /en/serverless/help/functions/event-functions/
---

# Create a Rule

Now that the Publisher and the Event Function are configured, let us define how the events should be processed and delivered by setting up a Rule.

Follow these steps to create the Rule:

1. In the Developer Console, select your project: *InvoiceNotifier*.

2. Go to **Catalyst Signals** and click on **Rules** in the left navigation.
![Add Rule](https://catalyst-docs-development.zohostratus.in/images/tutorials/invoice-notifier/rule.webp) 

3. Click **Add Rule**, then provide a name and description for your rule.
![Provide name and description for the Rule](https://catalyst-docs-development.zohostratus.in/images/tutorials/invoice-notifier/create-rule.webp)  

### Define Event Source

4. Under Source, click **Choose Event**, and select the Zoho Books Publisher you added earlier.

5. From the list of available events, choose *Customer Payment Created*, then click **Done**.
![Configure the publisher and event for the rule](https://catalyst-docs-development.zohostratus.in/images/tutorials/invoice-notifier/source.webp)  

### Define Event Filter

6. In the Filter section, click the **edit icon** and choose **Events matching certain conditions**.
![Select Events matching certain conditions](https://catalyst-docs-development.zohostratus.in/images/tutorials/invoice-notifier/filter.webp)  

7. Create a filter condition to include only events where the invoice status is **Paid**:
    - In the Path dropdown, select the JSON path that corresponds to the **payment_status** field.
    - Define the condition to match Paid.

8. Click **Save** to apply the filter.  
![Configure filter for the rule](https://catalyst-docs-development.zohostratus.in/images/tutorials/invoice-notifier/filter-criteria.webp)  

### Configure Target Settings

9. Click **Choose Target** and give your target a name.

10. Under **Consumer Type**, select the Event Function we created earlier using the CLI.

11. Set the **Dispatch Policy** to **Batch by Interval**:
    - Choose an interval of *one hour*.
    - Set the Retry Count to *five*.
![Configure target settings](https://catalyst-docs-development.zohostratus.in/images/tutorials/invoice-notifier/target-settings.webp)  

### Transform the Payload

12. In the **Target Input** section, choose **Transform**.
     
13. From the default event payload of the *Customer Payment Created* event, select only the required data and structure them as shown below. 

**Expected Event Payload**

```json
{
    "data" : [
        [
            {
                "Customer" : "test",
                "Invoice Number" : "Customer opening balance",
                "Amount" : "₹3,24,244.00",
                "Paid On" : "31/10/2023",
                "Invoice Id" : "275557000000158181"
            }
        ]
    ]
}

```

**Data Mapping for Template Compiler**

```text
{
    "data" : $.events.forEach((event)->
        event.data.payment.invoices.forEach((invoice)->
            {
                "Customer" : event.data.payment.customer_name,
                "Invoice Number" : invoice.invoice_number,
                "Amount" : invoice.total_formatted,
                "Paid On" : event.data.payment.date_formatted,
                "Invoice Id" : invoice.invoice_id
            }
        )
    )
}

```

Paste this structure into the template compiler to extract the required fields and click **Generate Output**.

![Event Body Transformation](https://catalyst-docs-development.zohostratus.in/images/tutorials/invoice-notifier/transformation.webp)

Check out the [Even Body Transformation help guide](https://docs.catalyst.zoho.com/en/signals/help/targets/event-body-setup/event-transformation/) to learn how to customize event payloads in detail.

14. Save the target configurations, then click **Save** again to finalize the rule.

Now, whenever a customer completes a payment, the corresponding invoice in Zoho Books is updated. This update triggers an event that is processed every hour in Catalyst Signals and automatically sends a summarized message to the Zoho Cliq channel. 

![Invoice Notifier](https://catalyst-docs-development.zohostratus.in/images/tutorials/invoice-notifier/demo.webp)