MarketPress - Where can I add a TAX Deduction option

Hello,

I would like to add the option for people, that have a valid VAT number, to be able to add this to their info, so that they can deduct the tax/vat amount.

Is this function available? If so where do I find it?

Also if this function is available, does it automatically check with the VIES website if the VAT number provided is valid?

Best regards,

David