There are many reasons why you might choose to have an SEO Audit performed on your website.
If you already have in-house web developers this is a great way to get expert advice on what your site needs to perform at its best in the search engines however you can save on the implementation of these by passing the audit onto your own web developer for implementation.
Other reasons for requesting an SEO Audit could be that it has been a while since you have done any SEO and you want a detailed report on where you are ranking, what needs to be improved and what your competitors are up to.
An SEO Audit can also be useful if you have a very large site or an ecommerce site. A very large site is more difficult to SEO as the impact is diluted by the number of pages that your site has. An audit can identify the major changes and help to structure the implementation process so that scripting can be used to make changes to very large (1000 page plus) websites.
Ecommerce sites can also benefit from an Audit as a detailed report on the site navigation, conversion rates and sales funnels can provide invaluable information for the business owner.
Finally, multi-national companies who have sites in more than one language or country can also benefit from an SEO Audit to provide a helicopter view of how all sites fit together and work synergisticlly to support each ones rankings in the search engines without duplicate content issues.