What is confirmation statement?
A yearly filing telling Companies House its record of your company is still correct.
Once a year every company confirms that the details on the register (directors, registered office, shareholders, people with significant control) are still accurate. It costs £50 to file online.
It is not accounts and it is not a tax return. It is a separate obligation, on its own deadline, and it is one of the three annual jobs a company has that a sole trader simply does not.
Missing it is taken seriously: persistent failure to file can lead to the company being struck off.