Couples building a life together often want to put their relationship on a formal footing. This has many advantages.  A marriage or civil partnership is a sign of a couple's commitment to each other and, alongside the celebration, brings formal legal rights and tax advantages.

But some couples, such as Charles Keidan and Rebecca Steinfeld, don't feel that marriage is for them.  They want a Civil Partnership instead.

Before marriage equality for same sex couples, the introduction of Civil Partnerships in 2005 created legal recognition of the couple's commitment, with the same legal and financial rights as married heterosexual couples but without being legally recognised as a marriage.

The introduction of marriage equality didn't do away with Civil Partnerships, so a gay couple can pick either marriage or Civil Partnership.  The same choice is not available to heterosexual couples.

Mr Keidan and Ms Steinfeld will have to see whether the Supreme Court agrees that Civil Partnerships should be extended to heterosexual couples, and in the meantime they face the legal and tax planning issues about structuring their estate and planning their lives to work around the fact that they don't have a legally recognised relationship.

Without an automatic right to inherit from each other they should ensure they have wills in place to pass on assets should one of them die.  They will need to think about their inheritance tax position because they cannot claim spouse exemption and will only have their individual inheritance tax allowances to rely on.

They should also consider lasting powers of attorney so that if one of them loses the ability to make decisions an arrangement will be in place for that person's money to be managed.

All couples need to think about their estate planning, but without a marriage or civil partnership there can be additional complications if one person dies or struggles to make decisions for themselves.