If you or your partner dies, and you are registered Civil Partners, you do not have to pay a penny in inheritance tax.
If you gift your Civil Partner assets, such as company shares, there will be no Capital Gains Tax (just the same as for a married couple).
Same-sex Couples NOT Registered As Civil Partners
If you are in a same-sex partnership and have not registered under the Civil Partnership Act and you leave all your assets to the survivor, tax at 40% will be charged on the value over £325,000. Married couples and civil partners would not have to pay a penny.
If you do not make a will, your assets will not automatically go to your partner.
If you gift your partner assets, such as company shares, you may be liable to Capital Gains Tax - Civil Partners and married couples would be exempt.