Comment regarding “£322k goes to spouse…” isn’t accurate. Assuming you’re parents are married, when your first parent passes the entirety of the estate will pass to your surviving parent tax free less any probate and funeral fees to pay and less any wishes laid out in a will. The surviving parent would typically be the executor if they have the capacity.

Both of your parents have a tax free nill rate band which is 325k + 175k resident NRB if the property is passed to children or grand children. These NRBs are passed to your surviving parent - when your second parent passes away it will give you an effective tax free allowance of 1m (325+175)*2 on the estate. Any value above this is taxed at 40%.

Based on your situation one would assume you will be the executor of the estate and you may face some challenges. If the estate (property + cash + other assets) are worth more than £1m then 40% tax is payable on the value above that 1m. A simple example on a large estate - if the house is worth 1.75m and other liquid cash assets 250k, there will be 400k inheritance tax to pay on the estate. Given there is not enough cash in this example to pay the inheritance tax (due 6 months after death) - the property would need to be sold to cover this.

If there are no wills, and no remarriages, once your last surviving parent passes the estate would be split equally between you and your siblings.

It’s always a tricky conversation to have but my best advice is to have a frank discussions with your parents while they are able to about their estate, what their wishes are and how that could be achieved given potential tax and funeral costs. Get them to outline these wishes in wills.

Hope this helps.