Some products have different tax codes, for example fresh fruit and vegetables in some countries do not attract GST. This can be easily managed within Vend.
In the general setup page, you are asked to choose your default tax setting. This will apply to each product created unless you select a different rate on the product page.
Product variants must all have the same tax rate. If you change the individual tax rate on the product's main page (the parent product), all of the other variants will also be updated.

If you've got lots of products you need to update, you can update these using a CSV import. You'll need to change the value in the 'Tax_Name' field to match the name of the required tax rate.
Before starting, make sure you read our guide to editing products via CSV.

If you're using Xero, you might like to ensure the account you send sales of this product to has the same tax rate as the custom rate you've just set in Vend.
You can do this by adjusting the account sales code as well as the tax rate.
For example you:
Here is an article explaining how to override default Xero account mappings.