Several points to correct here.
Your CT600 return must be made within 12 months of the end of your accounting period (AP)
However your tax due must be paid a maximum of 9 months after the end of the AP. This means that if you haven't drawn accounts up by this time, the tax is paid on reasonable estimates and then corrected in later years.
In most cases there is no reason why a small business can't complete the return well before 9 months is up.
All of the above applies to coroporation tax and HMRC. Don't confuse this with the requirements of Companies House. The 'annual return' to them is nothing to do with money - it is an annual statement of who the directors are. Also you do have to lodge some financial statements with them - but nothing like the data required on the CT600 form. Remember that the Companies House info becomes public info - your dealings with HMRC is private between your company and HMRC and is designed to ensure the business pays the right amount of tax.
The small business tax rate is 20% (shortly to rise to 21% unless the Chancellor reverses an announced statement) if the annual profits is less than �300k. It is assessed against profits - not turnover.