Leave in advance requires a signed written agreement stating the amount and start date (parent or guardian also signing for under 18s), kept as an employee record, with deduction of unaccrued leave allowed on termination. Cashing out requires a separate signed agreement for each amount, stating the amount, payment and date, paying at least what the leave would pay, leaving at least 4 weeks' balance and not exceeding 2 weeks in 12 months, kept as an employee record, without undue influence.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.