I want to change to US Premium Version to UK version.

You may have 2 options:

1. Utilize the 3rd party tools for self migrate

https://transactionpro.grsm.io/qbd

https://partners.saasant.com/affiliate/idevaffiliate.php?id=5051_2

2. Purchase a 3rd party conversion service

Hope it helps.

Hi, @accounting301.

Thank you for posting here in the Community. I can share some insights into our QuickBooks Desktop products.

Currently, switching QuickBooks Desktop US version to the UK version is unavailable. Subscribing to another version requires to buy a new license number. You can install and run multiple versions and editions of QuickBooks on the same computer. You can open different versions at the same time, whereas different editions must be opened one at a time.

Let's download first the QBDT UK version on your computer. Here's how:

1. Go to this link: https://downloads.quickbooks.com/app/qbdt/products?productName=QuickBooks%20Desktop%20Pro&edition=&v.... 
2. Select UK in the country drop-down arrow. 
3. Choose product and year version. 
4. Hit Search.

     5. Tap Download. 

After that, you can now install the product. You have two options for installing QBDT either express or custom and network. And make sure that you already have the license number. Once verified, please check out this article for the detailed steps on how to install the product, depending on what install types, you want to use: Install QuickBooks Desktop.

Please browse through this article: Fix QuickBooks Desktop install errors. This link helps you with how to resolve any error codes in installing QBDT products. 

Also, you can use a third-party app to convert the product as by Fiat Lux - ASIA mentioned above. Feel free to leave a comment below if you have another concern. I'm always here to help.