Thanks for your question.
First of all, if your daughter and her partner presently hold the house jointly (as joint tenants) then each person's share would pass to the other upon death regardless of any direction made in the Will. If this is not what she wants then she should sever the joint tenancy by using Form SEV from the Land Registry (you will have to send it to them and if you have any questions about completing the form you should call their customer service number - they are very helpful):-
They will then hold their interests as tenants in common, meaning that their respective shares will pass according to their wills or under the intestacy rules. Her partner need not sign the form provided you follow the instructions.
If your daughter leaves and her partners stays in the property then your daughter can force the sale of the property by making (or posturing to make) an application to Court. If the partner cannot demonstrate sufficient finance to receive a mortgage offer to buy her out and transfer the equity in to his name then this may be her only option. A local solicitor would be able to do this for her and these orders are seldom refused by the Court.
In the absence of any express agreement there is presumption that the proceeds of sale are split equally, however if either party contributed more the financing of the purchase or has maintained the majority of the mortgage then this will be taken in to account and they will receive more of the proceeds of sale. It is usually better to negotiate and settle unless one party is being particularly unreasonable in their demands.
Needless to say, she should make sure that the mortgage payments are met (either by her, both, or just him) otherwise it will be reflected on her credit rating and may ultimately result in the lender making an application for possession themselves in the event of default.
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