50% of work pension pre or post tax

ANGLICANPAT

Afternoon All.  Its my understanding that   the married partner with LPA,  left in the  marital home  when their  OH with dementia needs to go into a  (NH)nursing home, can transfer  half of the NH partners work pension into their own account ,on which to live/run the couples home,  if say  the person in the NH has been the only earner over the years.  Does anyone know if the division is   made after the 'earner's    tax is taken or   before if  their tax brackets are very different ? Thanks.