Companies had until January 20 to provide the relevant information to the Motor Insurance Database as part of the new EU Fourth Motor Insurance Directive, part of a major anti-crime initiative.
Some 2.5 million fleet and motor trade vehicles have been registered, but latest estimates suggest that details for more 1.5 million vehicles have yet to be supplied. Officials at the Motor Insurers' Information Centre said that 50,000 policyholders had done 'nothing at all' to comply with the legislation.
If companies fail to provide details they can be fined £5,000 and currently, officials warn, fleets are exposed to fines worth hundreds of millions of pounds.
MIIC's programme manager Donald Martin said: 'The MIIC has spent a considerable amount of time and money advising the fleet community, motor traders and UK business in general that they could not ignore the legislation and to supply data as soon as possible.
'The Directive is now law and the policyholders who have yet to submit to the database must act now or risk facing fines of up to £5,000.'
Martin said it was imperative that fleet decision-makers contact their insurance companies or brokers if they are unsure about what to do to comply with the new law. The MIIC admits that its system for registering vehicles was subject to technical difficulties at launch caused, it said, by a surge of people supplying vehicle data immediately before and after the deadline. The company said the system now worked properly and had been stable for about a month.
Martin added: 'Bearing in mind that more than half of all policyholders should, in any case, have been supplying their data to insurers, most of whom offer a range of submission methods, policyholders now have no excuse for failing to submit their data.'
The MIIC's final warning comes soon after research carried out by leasing firms Interleasing and LeasePlan found that nearly half of all UK companies missed the directive deadline.
Registrations cannot be backdated, so fleets must plan well in advance to ensure vehicles are logged on the database in time. Furthermore, even if fleets have vehicles on the fleet for less than 14 days, they must keep detailed records spanning several years to meet the demands of the legislation.