HMRC estimates suggest around 10,000 companies will be affected by changes to the regulations for the tax and national insurance contribution (NIC) payments due from workers engaged via offshore intermediaries, which were laid out in the Budget 2013 and are set to raise some £80m annually for the Treasury.

The new measures include a record keeping and return requirement for intermediaries placing workers with end clients but not deducting income tax and NICs at source. They also introduce a certification system for employers when someone other than the deemed employer is administering and paying NICs, income tax and NICs through PAYE on the deemed employer's behalf.

Following a consultation earlier this year on offshore employment intermediaries, which indicated that a large majority of respondents thought the original proposals too complex, the government issued a revision. The new rules will become effective from 6 April 2014.

In its latest Tax Information and Impact Note, HMRC estimates the changes will produce a gain of £80m a year for the Exchequer in 2014-15, rising to £90m annually by 2017-18. It estimates they will have an impact on approximately 10,000 businesses, which will now have to assure their supply chain and fulfil new record keeping requirements.

These requirements include businesses submitting a quarterly return to HMRC which provides details of workers they place with end clients but for whom they do not deduct income tax and NICs at source. HMRC says the total cost of this increased administration requirement is expected to be approximately £800,000 per year.