can a reg no on retention from this country be registered in belgium without many issues or extra costs !!

thanks in advance

 

I don't think so because you can't register a UK number abroad, and a foreign-registered car can only be kept in another country for up to 12 months before it needs re-registered in its new home - governments everywhere all want to collect their road tax or local equivalent.

For a lot of countries, it's only 6 months.