What does NEC4 clause 60.1(21) mean?

In the NEC4 main contract it lets the Client add to the list. On an NEC subcontract, read the Client as your main contractor, and check what your Contract Data adds. One Contract Data entry lets extra compensation events be stated. Anything written there counts the same as the 20 numbered paragraphs, with no need for a Z clause. Typical additions are risks the other side is better placed to carry. Examples are a utility company's delay beyond a stated date, or contamination beyond a stated level. But the wording is whatever was written. An event drafted loosely is generous. One written with conditions is only as wide as those conditions. A blank entry adds nothing. To rely on the clause, show the Contract Data entry, that what happened is the event it describes, and that any conditions in it are met. Notify under clause 61.3 within 8 weeks of becoming aware it has happened. The exception is an entry describing an event that comes from the other side's own instruction or decision, which it should notify. The change to the Prices, your contract price, is assessed under clause 63.1, exactly as for the numbered events. It is the effect on actual Defined Cost up to the notification and forecast Defined Cost after it, plus the Fee. The decision under clause 61.4 applies in the same way. Two things go wrong most. You assume the standard list is the whole list and never read the Contract Data, so an event the other side expressly accepted is never notified. Or an extra event overlaps a numbered paragraph, and you notify under the wrong one. Any delay to the Completion Date is assessed separately under clause 63, and that is a job for your planner.