FHDDS25400 - Policy and background: due diligence: record keeping
(The Fulfilment Businesses Regulations 2018, regulation 10)
Due diligence records, along with other records an approved person must keep, must be kept for a period of six years. They must also be made available for inspection by HMRC on request.
Failure to undertake or keep records is liable to a penalty of up to £500 per contravention.