The tax authorities in Spain are warning UK companies of the obligation to appoint a fiscal local representative for compliance and reclaims if there is a no deal Brexit after 29th March 2019.
If the UK leaves the EU it would leave the EU VAT regime too. UK companies would need to then appoint a fiscal representative for ongoing local VAT filings and reclaims.
For filings or compliance the fiscal rep will either be jointly/severally liable for remitting, charging and record keeping for VAT.
These VAT agents would be charging larger fees and also a bank guarantee to protect them as they would have shared VAT liability.