I am trying to start preparing accounts for client but he did set up QB by himself and accounting period is wrong and it is look like he set up himself as VAT registered when actually he is not. His expenses are showing net value and VAT control is showing in trial balance.
The option to turn off the VAT feature in QuickBooks is unavailable. However, there's a workaround I can show you which would be the same as having the VAT turned off because it will no longer post anything to your VAT center. This is done by setting up your default VAT code as no VAT. I'll show you the steps on how to do that.
In your QuickBooks Online account, click on the company Settings or Cog.
Select Account and Settings.
Under the Accounting section, click the edit icon.
Change Default tax rate selection to No VAT.
Select Save and Done.
I've also added a screenshot for your additional reference.
Moving forward, no VAT will be recorded at all and this will not count toward your VAT returns that are filed through QuickBooks. Feel free to visit this reference page to learn more about setting up VAT in QuickBooks Online: VAT for QuickBooks Online UK. This contains VAT articles that may help you along the way such as remove a VAT rate and record a VAT payment or refund in QuickBooks.
You can always tag my name in the comment section below if you have other concerns or questions. I'd be happy to help. Take care and have a wonderful day.