I am using ERPNEXT for sales of used goods.
Here in Germany this leads to using a special tax rule.
As seller you only have to pay VAT on the PROIFT you make with a particular sale.
Purchase price: 100 EUR
Sales price: 130 EUR
PROFIT to be taxed: 30 EUR
19% of VAT included in the revenue : 4,79 EUR
On booking the sales invoice with the total revenue ERPNext should calculate the PROFIT TAX. The original purchase price is referenced via the serial number of the product.
So all data should be available when booking the sale. I simply don´t know how to start here.
Thanks for your suggestions