ICAEW is warning that companies have just twelve months to prepare for 'the biggest change in UK financial reporting in a generation' when the new UK GAAP - FRS 102 - comes into force on 1 January 2015, and says companies need to take account of new data requirements.

Dr Nigel Sleigh-Johnson, head of ICAEW's financial reporting faculty, said: 'The transition to the new reporting standards is perhaps the greatest accounting change non-listed UK companies have faced for about 40 years.

'Preparing the move to the new regime may require considerable time and resource. It is critical that companies start thinking about it now if they haven't already. Failing to do so could mean more pain and less gain when they change over to the new rules.'

The institute says that companies may need to start collecting data from the beginning of this year since they will be required to provide comparative information when preparing their first financial statements under the new accounting framework.

Some of this information will be much easier to obtain at the time the relevant activity takes place, so ICAEW is urging companies to collect such data and information as they go along during 2014. One example is capturing the valuations for certain investments and derivative contracts when the transactions happen, in order to report fair value later.

Sleigh-Johnson said: 'It is important to establish the extent to which each company will be affected. The transition may require additional training of staff, systems updates and new software. It may also affect bank covenants, and bonus and tax payments, which means there should be early communication with staff, lenders and investors.'