Persons who are non-domiciled in the UK, but have a UK domiciled spouse or civil partner can now opt to be domiciled in the UK.

This has various tax considerations, amongst them they will now be able to receive gifts from their partner during their lifetime free from inheritance tax, although it should be noted that individuals who are UK domiciled will be liable to UK inheritance tax on their worldwide assets. If you are not UK domiciled then you are only liable for UK inheritance tax on assets situated in the UK. Also once you opt to be UK domiciled then any transfers to persons other than your partner will also be liable for UK inheritance tax. Again if you are non-UK domiciled then only transfers on UK assets will be liable.
Previously non-UK domiciled were only considered UK domiciled for inheritance tax purposes if they had been UK domiciled for a three year period prior to any transfer or if they had lived in the UK for a seventeen out of twenty years ending with the year of assessment in which the transfer takes place. However as of 6 April 2013 if the individual is married or in a civil partnership with a UK domiciled person then they will be able to opt to be treated as UK domiciled for inheritance tax purposes.
The Finance Act of 2013 is awaiting Royal Assent and once this is received persons wishing to make this election may do so in writing to HM Revenue & Customs. This option can be taken during both individuals lifetime or after death. If a person is making this option after the death of their partner it should be noted that this will only be valid if made within two years of the death and the death must have occurred on or after 6 April 2013.
Persons that elect to be treated as UK domiciled to take advantage of the benefits of being able to receive gifts from their partner tax free should note that they will not be able to revoke this whilst they remain resident in the UK. If the individual is resident outside the UK and paying income tax for more than four full consecutive years at any time after they make the election then this will cease to have effect from the end of the forth year.