How to get proof of employment history
A special employment history request can be submitted by taxpayers for those needing to make a claim for compensation. The form is usually used for claims relating to industrial injuries, road traffic accidents, medical negligence and hardship.
HMRC will only accept requests that are made using the Employment history team: claimant’s evidence of employers form. The form is available on the GOV.UK website.
There is an additional form that must be completed where an application is being made for a deceased relative's employment history. This form should only be completed in full by the person legally entitled to apply for the Grant of Probate or Letters of Administration as this may not necessarily be the next-of-kin.
HMRC has 40 calendar days to reply to request for information. Where taxpayers are contacted for additional information the 40 days starts after HMRC receives the additional information. HMRC asks that taxpayers do not to contact them for an update on the status of a claim unless the 40-day limit has passed.
Source: HM Revenue & Customs | 14-02-2018