I need to create new VAT code for before the 1 April 2015 from 14% to 15 %

Hi there, mike.

We're glad you've joined us here in the Community. 

Yes, you may need to create a new vat code in QuickBooks Online for the new tax rate. Here's how:

1. Go to the Taxes menu, then click Add tax. 
2. Select Tax rate.
3. Enter all necessary details including Tax name and Description.
4. Type in the new tax rate that'll be effective April 1.
5. Select the right Account.
6. Click Save.

You can also take a look at the screenshots below or visit this Help article for more details: https://community.intuit.com/articles/1186465. 

Let me know if you have other questions. We're here to help. 

Create new tax under Taxes then add tax.