Tax calculation Drupal Commerce
The Commerce Price Components module allows you to change what elements of a price are included when displaying it, including whether tax is included in the amount.  With that module, you can get the result you are looking for by editing the view behind your Checkout screen (from your screenshot).


Go to the Checkout screen so it looks like your screenshot.  In other words, be sure you have a VAT tax set up, and a product in your shopping cart, and go to Checkout.  The screen will look as you show above, ie the line item price will INCLUDE VAT.
There is a gear icon in the upper right of the screen (above the word TOTAL).  Hover over this and click EDIT VIEW.
You will be in the Commerce Cart Summary View.  In the FIELDS list, click on the Commerce Line Item Unit Price.
Change the Formatter to Price By Components, and be sure only Base Price is ticked.
Click APPLY
Do the same for the Commerce Line Item Total.
Click SAVE to save the View