An SEO audit is an important task that should be conducted every so often in order to keep your site competitive and your SEO plans on track.
It can help you to uncover vital errors that may be negatively impacting your rankings in the SERPs, including on-site issues, penalties your site is incurring, technical errors, issues with speed, security issues, site architecture, duplicate content issues, broken links and more.
There are many tools available that can help you conduct an SEO audit or you can do one manually yourself however, the best way, in most cases, is to have a team of professionals audit your site for you. This will ensure you are getting the best available suggestions and receiving help with the implementation of changes.