The requirements and documentation needed to pay NHS pension as a Locum is currently changing so fast we feel it is best to direct you to the NHS Pension Agency website for the most up to date information. 
You should find the relevant forms and payment instructions detailed here.
https://www.nhsbsa.nhs.uk/member-hub/information-practitioner-locum-and-non-gp

Other useful sites regarding Locum pension payments include -
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