21.2. If the non-delivery of any of the goods prevents the normal use of the supplies as a whole, the liquidated damages provided for in Article 21.1 shall be calculated on the basis of the total contract price. 

21.3. If the contracting authority has become entitled to claim at least 15% of the total contract price it may, after giving notice to the contractor: 

## Article 22 - Amendments 

 seize the performance guarantee; and/or 

terminate the contract, 

 enter into a contract with a third party for the provision of the balance of the supplies at the contractor's cost. 

22.1. Contract amendments must be formalised by a contract addendum signed by both parties or by an administrative order issued by the project manager or the contracting authority. Substantial amendments to the contract, including amendments to the total contract price, must be made by means of an addendum. Any contractual amendments must respect the general principles defined in the practical guide. 

22.2. Subject to the limits of the procedure thresholds set in the practical guide, the contracting authority reserves the right to vary by an administrative order the quantities per lot or per item by +/- 100 % at the time of contracting and during the validity of the contract. The total value of the supplies may not rise or fall as a result of the variation by more than 25% of the tender price. The unit prices quoted in the tender shall be applicable to the quantities procured under the variation. 

22.3. The project manager and the contracting authority shall have the power to order any amendment to any part of the supplies necessary for the proper completion and/or functioning of the supplies. Such amendments by administrative order may include additions, omissions, substitutions, changes in quality, quantity, form, character, kind, as well as in drawings, designs or specifications where the supplies are to be specifically manufactured for the contracting authority, in method of shipment or packing, place of delivery, and in the specified sequence, method or timing of implementation of the tasks. No administrative order shall have the effect of invalidating the contract, but the financial effect, if any, of all such amendments shall be valued in accordance with Article 22.7. 

22.4. All administrative orders shall be issued in writing, it being understood that: 

a) if, for any reason, the project manager or the contracting authority finds it necessary to give an order orally, it shall as soon as possible thereafter confirm the order by an administrative order; 

b) if the contractor confirms in writing an oral order given for the purpose of Article 22.4.a and the confirmation is not contradicted in writing forthwith by the project manager or the contracting authority, the project manager or the contracting authority shall be deemed to have issued an administrative order; 

c) no administrative order is required to increase or decrease the quantity of any incidental siting or installation because the estimates in the budget breakdown were too high or too low. 

22.5. Save where Article 22.4 provides otherwise, prior to issuing an administrative order, the project manager or the contracting authority shall notify the contractor of the nature and form of such amendment. The contractor shall then, without delay, submit to the project manager a written proposal containing: 

