---
title: UltraTax CS Running Slow, Freezing, or Lagging – Complete Fix Guide
description: "UltraTax CS runs slowly, freezes frequently, lagging or becomes unresponsive while working on client returns. Users may experience: - Delay opening client files - Freezing during data entry - Slow switching between screens - Lag when accessed remotely - Overall…"
url: "https://www.oneupnetworks.com/knowledgebase/performance-speed-stability/ultratax-cs-running-slow-fix/"
updated: "2026-02-15"
category: "Performance, Speed & Stability Issues"
tags:
  - Thomson Reuters
---

# UltraTax CS Running Slow, Freezing, or Lagging – Complete Fix Guide

UltraTax CS runs slowly, freezes frequently, lagging or becomes unresponsive while working on client returns. Users may experience:

- Delay opening client files
- Freezing during data entry
- Slow switching between screens
- Lag when accessed remotely
- Overall poor performance during tax season

This issue significantly reduces productivity and increases frustration, especially when working with multiple clients.

## Causes for UltraTax (UT) Slowness

The most common causes include:

- Insufficient system RAM or CPU
- High server load from multiple users
- Network latency or slow internet
- Antivirus software scanning UltraTax files
- Corrupted temporary files
- Improper workstation configuration

## Resolution

Follow the steps below in order.

### Step 1: Restart UltraTax and Workstation

- Close Thomson Reuters UltraTax CS completely.
- Restart your computer.
- Reopen UltraTax and check performance.

This clears temporary memory and resolves minor software conflicts.

### Step 2: Exclude UltraTax from Antivirus Scanning

- Antivirus scanning significantly slows UltraTax performance.
- Add exclusions for these folders:

```
     X:WinCSI
     X:UltraTax
```

Contact your IT administrator if needed.

### Step 3: Check System Requirements

Minimum recommended:

- RAM: 16 GB (32 GB recommended for multiple users)
- Processor: Intel i5 or higher
- SSD storage (not HDD)

Insufficient hardware is one of the most common causes of slow performance.

### Step 4: Disable UltraTax Home Page Auto-Load

Steps:

- Open UltraTax CS
- Go to: Setup → User Preferences → Miscellaneous
- Uncheck: Show Home Page at Startup
- Click OK

This improves startup speed.

### Step 5: Clear Temporary Files

- Navigate to: C:\WinCSI\UTYYDATA\
- Delete temporary files (.TMP)

Do NOT delete client folders.

### Step 6: Check Internet Speed (For Remote or Hosted Users)

Minimum recommended:

- 50 Mbps internet speed
- Latency below 20 ms

Slow internet causes delays, freezing, and input lag.

---

### Prevention

To prevent future slowdowns:

- Restart system weekly
- Use SSD storage
- Maintain sufficient RAM
- Exclude UltraTax from antivirus
- Avoid overloading shared servers

---

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