Local government units may be required to use cash registers for the purposes of recording transactions with natural persons who do not conduct business activity.
Receipt and invoice
If the invoice concerns a sale recorded using a cash register, a receipt documenting the sale is attached to the copy of the invoice remaining with the taxpayer (seller).
In the case of a recorded sale using a cash register confirmed by a fiscal receipt, an invoice for the VAT payer (under penalty of sanctions) is issued only if the receipt includes: NIP number of this taxpayer or the number by which the taxpayer is identified for VAT purposes.
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Source Deloitte
