Pay instead of notice

Sometimes it is in both your interests not to work out the rest of your notice period.  You can agree with your employer that you can leave as soon as you are given notice in return for lay in lieu of notice.  This is often called "gardening leave".

You should still receive your full entitlements as if you were working out your notice.

This link takes you to the HM Customs web page, explaining the tax implications

Tax on pay in lieu of notice

Note that if an employer dismisses you without payment, then the employer is in breach of contract and you can sue for the wages that you would have received if notice had been given. 

Some employers are prepared to pay this sum gross, rather than net, but entitlement depends on the contract of employment.