VAT from profit

[MellRebook]

Hello!

 

I'm in middle of developing and configuring shop for my client.

 

I was ordered to configure prestashop to calculate tax from profit (in Poland it is used when selling second-hand items: cars, jewellery etc.)

 

I have no idea how to do it. I had found function in classes/tax/TaxCalculator.php called addTaxes($price_te).

My problem is, how to get beginning price there.

It should look something like this:

 

$taxValue = ($sellPrice - $beginningPrice)*$taxRate;

In this function I probably have only access to sell price value.

 

Any help appreciated!

PrestaShop v.1.6.0.9