An annual return is a general information about the company's directors, shareholders, nature of business (SIC code) and registered office address. It must be filed within 28 days of the anniversary of incorporation of the company.
All UK companies must file an annual return to Companies House every 12 months. If not filed on time, Companies House will issue a penalty.
You can see the list of SIC codes here:
CG Incorporations Limited can help you in filing your Annual Return for £50.