My mother bought an apartment in spain with her partner 7 years ago, he died 5 years ago. In his will he left his share to her, but nothing has been done officially to change the ownership. She may need to sell the apartment in the next two years. Should she change the deeds/ownership to her name before she sells, and if so how much tax would she have to pay? Or should she wait until she sells? what tax would she be liable for then?

Thank you for yur help in this