How To: Tell Google about your domain change
If you’ve recently moved your site to a new domain, you can use the Change of address tool under the Google Webmaster Central dashboard to tell Google about your new URL. This will allow Google to update their index to reflect your new URL. Changes will stay in effect for 180 days, by during that time Google will crawl and index the pages at your new URL.
The change of address tool is safe to use as its backed up by Google’s site verification. So only the real site owners will be able to use it.
Note: If you’ve specified a preferred domain for your original site, you should also set it for your new site.
In order to use the change of address tool, make sure that you’ve added and verified both your old and new sites in your Google Webmaster Central Dashboard. In addition to that, make sure your original site is not a subdomain (for example, http://newwebsite.example.com).
Access Change of address from:
1. On the Webmaster Tools Home page, click the site you want.
2. Under Site configuration, click Change of address.
3. In Step 4, in the Select a verified site list, select the new site.
Google posted a help document on moving your domain to assist webmasters with this process.