---
title: "How to Identify Customer Replies by Invoice Number in Estimate and Invoice Emails?"
slug: "how-to-identify-customer-replies-by-invoice-number-in-estimate-and-invoice-email"
updated: 2026-10-15T00:56:19Z
published: 2026-10-15T00:56:19Z
canonical: "help.servicetitan.com/how-to-identify-customer-replies-by-invoice-number-in-estimate-and-invoice-email"
---

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

# How to Identify Customer Replies by Invoice Number in Estimate and Invoice Emails?

## **Problem**

You don't know which estimate or invoice an email corresponds with.

## **Solution**

### Add the {InvoiceNumber} and {EstimateNumber} placeholders to your Emails

Placeholders let you add customer-specific content to your templates. If you want to know which invoice or estimate you're referring to when sending multiple emails, add the {InvoiceNumber} and {EstimateNumber} placeholders to the **Subject** fields of your Invoice and Estimate email templates.

1. Go to Settings ![A simple icon representing a settings gear. ](https://cdn.document360.io/961862ab-d0f2-4d91-bb62-a62ee8184eff/Images/Documentation/icon-gnav-settings-inactive.png?sv=2026-02-06&spr=https&st=2026-10-31T03%3A48%3A03Z&se=2026-10-31T04%3A48%3A03Z&sr=c&sp=r&sig=LKMBoemNwBlC4CvP%2FLJF2l4yLk5wDF6I6OMuTnzv5Vk%3D).
2. Go to **Invoicing** > **Email**.
3. On the Email settings screen that opens, select the email template you wish to edit.
4. To include the invoice number in the subject line of your invoice emails, copy and paste the {InvoiceNumber} placeholder into the subject line. You can also include the {InvoiceNumber} in the body of the email.
5. To include the estimate number in the subject line of your invoice emails, copy and paste the {EstimateNumber} placeholder into the subject line. You can also include the {EstimateNumber} in the body of the email.

This way, when a customer responds, you'll immediately know which invoice the reply pertains to.