How does JCT clause 4.13 work?

Clause 4.13 of SBC/Q 2016 is the contract's version of section 112 of the Housing Grants, Construction and Regeneration Act 1996. The contract right and the statutory right run together. It lets the Contractor suspend any or all of its obligations, in three parts. First, the failure. The sum due has not been paid in full by the final date for payment. The sum due is the notified sum, less anything in a valid Pay Less Notice. Second, the notice. The Contractor gives written notice to the Employer, copied to the Architect/Contract Administrator, of its intention to suspend and the grounds. Only if the failure continues for the period the clause gives after that notice may it suspend, and only until it is paid in full. Third, the consequences. The Contractor is entitled to a reasonable amount for the costs and expenses it reasonably incurs because of the suspension. A suspension under clause 4.13 is also a Relevant Matter under clause 4.22, so the loss and expense route is open for the effect on progress. Any effect on the completion date is dealt with separately, under the extension of time clauses and by a planner. Five things go wrong. The Contractor suspends before the final date has passed. It suspends over a disputed sum, not a notified one. It sends the notice to the Quantity Surveyor instead of the Employer. It stops before the notice period has run. Or it keeps no daily record of the demobilisation, standing time and remobilisation costs the clause is there to pay. On a JCT subcontract, check its own suspension clause and notice period.