JCT variations vs NEC compensation events

Published 14 June 2026 · VariationFlow

JCT and NEC handle change in fundamentally different ways. A side-by-side guide to variations under JCT versus compensation events under NEC3/NEC4, terminology, process, valuation and timescales.

JCT and NEC are the two dominant contract families in UK construction, and they treat change very differently. Run a project on the wrong assumptions and you can lose entitlement. Here is how they compare.

Terminology

JCT calls instructed change a 'Variation'. NEC has no variations at all, it uses 'compensation events', a broader category covering instructed changes to the Scope (NEC4) or Works Information (NEC3) along with other listed events such as certain delays and physical conditions.

Who instructs, and how

On the main contracts, the Architect or Contract Administrator issues instructions under JCT and the Project Manager under NEC. On a subcontract under either family your instructions come from the contractor above you, and on the NEC4 subcontract it is the Contractor that instructs you and actively manages your compensation events. NEC is built around proactive, early communication rather than back-end settlement.

Valuation

• JCT: valued against the contract rates and prices, with pro-rata rates, fair rates or daywork where no comparable work exists
• NEC: assessed on the effect on Defined Cost plus Fee (actual or forecast cost plus the fee), via the contractor's quotation

In short: JCT leans on pre-agreed rates; NEC leans on cost.

Time and money: together or apart

Under NEC, a compensation event assesses time and money together in a single quotation, the programme effect and the cost effect are dealt with at once. Under JCT, the money (loss and expense) and the time (extension of time) are generally handled as separate processes.

Timescales, and why they bite

This is the big practical difference. NEC sets strict time limits for notifying and quoting compensation events. Notify late and, in many cases, you lose your entitlement, the contract is unforgiving by design. JCT is generally less time-critical on variations, though notice provisions for loss and expense still matter. On NEC, notifying on time is often the difference between getting paid and not.

What this means on site

Whichever contract you are on, the winning behaviour is the same: capture every instruction and change as it happens, with evidence, and act within the contract’s timescales. NEC just punishes a lack of discipline faster.