The HMRC guidance states that before making a first payment, the contractor should be satisfied that the engagement is one of self-employment. Suggestions are made of contacting HMRC or using the Employment Status Indicator (ESI). This is guidance and not law, and of course there are other sources of advice. Nothing is stipulated as to how this satisfaction should be documented.
5.3.2 Making a verification
HMRCʼs system is set up so this should be made online. This can be by use of its own software or that of a commercial provider. See notes below about telephone verification.