---
title: "Can't clear a serialized item from an invoice because the serial number is required"
slug: "how-to-add-serial-numbers-to-adjustment-invoices-and-returns"
updated: 2026-10-15T00:48:11Z
published: 2026-10-15T00:48:11Z
canonical: "help.servicetitan.com/how-to-add-serial-numbers-to-adjustment-invoices-and-returns"
---

> ## 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.

# Can't clear a serialized item from an invoice because the serial number is required

![](https://cdn.document360.io/961862ab-d0f2-4d91-bb62-a62ee8184eff/Images/Documentation/anvil-wrench.png?sv=2026-02-06&spr=https&st=2026-10-31T01%3A49%3A46Z&se=2026-10-31T02%3A49%3A46Z&sr=c&sp=r&sig=v7w4E6vrJwu3O0rZOl2UfTGRh%2F%2FYUCpgD6Agy6V5rI4%3D) Troubleshooting **Role:** Inventory & procurement managers · Accountants**Area:** Accounting · Inventory · Serialized Inventory · All versions · All business types

## **What you're seeing**

You're trying to clear or correct an invoice that has a serialized piece of equipment on it — for example, by adding the equipment back at a negative quantity to zero out the cost. When you try, ServiceTitan requires a serial number to add that equipment, but it won't accept the original serial number. Once a serial number has been used on an invoice with its item, the system blocks that same serial from being added to any later transaction, including returns and adjustment invoices.

## **Why this happens**

**Reason 1**

**A serial number can only be used once.** Serialized inventory tracks each unit by a unique serial number across its whole life cycle, so once a serial number is consumed on an invoice, the system won't let you re-enter that exact serial on another transaction. That's what blocks the straightforward negative-quantity correction.

## **Before you start**

- You need permission to create adjustment invoices and inventory adjustments. If you don't have it, contact your administrator.
- Consider keeping a dedicated non-inventory item in your Pricebook for these cost corrections, rather than reusing a real item.

## **How to fix it**

The original article's method has two parts: create an adjustment invoice to bring the cost down, then create an inventory adjustment to bring the item and its serial number back to Available.

### **1****Create an adjustment invoice to bring the cost down**

1. Find and go to the invoice.
2. On the invoice screen, click **Add an adjustment invoice**.
3. On the adjustment invoice, add a non-inventory equipment/material with the same cost but in a negative quantity. This pushes the job cost down by the matching amount.

> [!NOTE]
> **✓ Next ·** With the cost brought down, continue to step 2 to restore the item and its serial number to inventory.

### **2****Create an inventory adjustment to restore the item and serial**

1. On the navigation bar, click **Inventory**.
2. In the side menu, click **Adjustments**.
3. On the Adjustments screen, click **Create New**.
4. On the Create adjustment screen, add the item used on the original invoice.
5. In the **Serial Numbers** column, enter the serial number and add a hyphen at the end.

> [!NOTE]
> **✓ Done ·** The original article states this brings the item quantity and the serial number back to **Available** in the warehouse.

## **Still not working?**

Contact ServiceTitan Technical Support at [**go.servicetitan.com/ask**](https://go.servicetitan.com/ask) with:

- The invoice number and the serialized item/equipment involved
- The original serial number and what the system does when you try to re-enter it
- Whether your tenant has the Automated Refund Workflow enabled
- Which steps from this article you already tried

## **Want to learn more?**

[**Create, edit, and copy inventory adjustments ›**](https://help.servicetitan.com/construction/docs/create-edit-and-copy-inventory-adjustments) Full walkthrough of building and managing the inventory adjustments used in step 2.

[**Edit serial numbers in your pricebook ›**](https://help.servicetitan.com/construction/docs/edit-serial-numbers-in-your-pricebook-1) How to view and correct serial numbers on items in your Pricebook.

[**Get started with serialized inventory ›**](https://help.servicetitan.com/construction/docs/get-started-with-serialized-inventory) Overview of how serialized inventory tracking works and how serials move through their life cycle.