At what point is a PIP claim valid?

I am just hypothetically thinking about someone who may inadvertently put themselves forward as a self selector…

Would a PIP claim be valid so long as all relevant information was provided during the initial phone call? Or is it the case that there are docs to be returned/signed before claim is valid?

Think I’ve dug out the answer to this in case anyone is interested; reg 11(4) of the UC,PIP, JSA, ESA (C&P) regs 2013

“(4) A claim made by telephone in accordance with paragraph (1) is properly completed if the Secretary of State is provided during that call with all the information required to determine the claim and the claim is defective if not so completed. “