The UK tax authority specified the procedure for providing CbS reporting

The UK's Majesty's Revenue and Customs (HMRC) has published a guide to preparing CbC (country-by-country) reporting.

The owners of multinational companies are required to send CbC reporting for each country with a detailed description of their activities. The report will be required if the group of companies has a consolidated income of 750 million EUR.

To submit a report, you must create an XML file that corresponds to the OECD scheme. Then it must be forwarded to HMRC through a special portal. The portal will start working in the near future. As noted in the HMRC, the formation of an XML file can be started now.

The obligation to submit a CbC report is effective for reporting periods beginning on or after 1 January 2016. It must be provided no later than 12 months from the end of the reporting period.
For admission of reporting period shall be imposed a fine of £ 300, for the provision of false information - up to £ 3,000.

A source: https://www.gov.uk/guidance/complete-your-country-by-country-report-correctly