To change your contact details:
follow the 'Your details' link from the left hand navigation menu on the 'Account overview' screen
follow either the 'Change address' or 'Change contact details' link on the 'Your details' page. To change your contact details for VAT you will be prompted to follow the 'Change registration details' link on this page
Please note: Email address changes made using the dashboard will only change the details for the specified tax record. If you want to change the email address for your Government Gateway online account, please log in and follow the 'Change details' link in 'Your account' which you can access from the left hand navigation menu on the 'Your HMRC services' page.