Hi Gabs,
If an online letting agent is providing an intermediary service to you as an overseas business then this would normally come under the General Rule of Services Rule and would be Outside the Scope of VAT.
Please see the guidance below:
11. Intermediary services.
If the VAT has been charged incorrectly then it would be the responsibility of the supplier to amend this, to raise a credit note and to amend their VAT returns.
Please see the guidance below:
4. Correcting VAT errors on a return already submitted
However if you are an overseas business and you are making supplies of land/property in the UK then the Place of Supply of your service will be in the UK if the property you are letting out is in the UK.
Please see the guidance below:
7. Land related services
If you are renting out holiday accommodation then this be a taxable supply in the UK.
Please see the guidance below:
1. Overview - hotels-holiday-accommodation-and-vat-notice-7093#overview
There will therefore be a requirement to register for VAT in the UK.
Please see below:
3. Working out whether you need to register
Who should register for VAT (VAT Notice 700/1)
Thank you.