Error on the VAT number of the assignee only formal until the end of 2019.

• The absence or inaccuracy of the VAT identification number of the buyer on the invoice does not prevent the actual buyer from being identified.
• The VAT identification number is an essential element of the invoice to identify the taxpayer.
• Starting from January 1, 2020, the VAT identification number of the buyer is a substantial condition for taxing the transaction in the destination member state.

Source: eutekne.info

Note that this post was (partially) written with the help of AI. It is always useful to review the original source material, and where needed to obtain (local) advice from a specialist.