Supplier claiming VAT from before registration

Our supplier was sending us invoices without VAT. They registered for VAT on 24.12.2023, but the registration took effect from 01.04.2022. Now they sent us a VAT only invoice claiming VAT on all invoices issued up to date. Are we legally required to pay that VAT invoice?

Hi Alex OPX,
There is no legal obligation to pay the VAT on this as it was not charged at the time of the supply.
However if you are VAT registered and agree to pay the VAT then you would normally be able to recover the VAT as input tax subject the normal rules of VAT recovery.
Please see below:
10. Introduction to input tax
Thank you.