excise tax or duty or rate increase was included in the contract price as a contingency reserve or otherwise; or

(2) Results in the Contractor not being required to pay or bear the burden of, or in his obtaining a refund or drawback of, any such Federal excise tax or duty which would otherwise have been payable on such transactions or property or which was the basis of an increase in the contract price, the contract price shall be decreased by the amount of the relief, refund, or drawback, or that amount shall be paid to the Government, as directed by the Contracting Officer. The contract price shall be similarly decreased if the Contractor, through his fault or negligence or his failure to follow instructions of the Contracting Officer, is required to pay or bear the burden of, or does not obtain a refund or drawback of, any such Federal excise tax or duty.

(c) No adjustment pursuant to paragraph b above will be made under this contract unless the aggregate amount thereof is or may reasonably be expected to be over $100.00.

(d) As used in paragraph b above, the term "contract date" means the date set for the bid opening, or if this is a negotiated contract, the date of this contract. As to additional supplies or services procured by modification to this contract, the term "contract date" means the date of such modification.

(e) Unless there does not exist any reasonable basis to sustain an exemption, the Government, upon request of the Contractor, without further liability, agrees, except as otherwise provided in this contract, to furnish evidence appropriate to establish exemption from any tax which the Contractor warrants in writing was excluded from the contract price. In addition, the Contracting Officer may furnish evidence to establish exemption from any tax that may, pursuant to this Clause, give rise to either an increase or decrease in the contract price. Except as otherwise provided in this contract, evidence appropriate to establish exemption from duties will be furnished only at the discretion of the Contracting Officer.

(f) The Contractor shall promptly notify the Contracting Officer of matters which will result in either an increase or decrease in the contract price, and shall take action with respect thereto as directed by the Contracting Officer.

The following is an amplification of Clause 4, Differing Site Conditions, as provided for in Section 1-18.117, Federal Procurement Regulations:

ADMINISTRATION OF THE DIFFERING SITE

CONDITIONS CLAUSE

(a) Nature of the clause. The Differing Site Conditions clause in Section 1-7.602-4 provides for an equitable adjustment to the contractor or the Government which reflects the increases or decreases in a contractor's cost of and time for performance that result from a differing site condition (as that term is defined in the clause) encountered by the contractor. However, an equitable adjustment is only available to the contractor if he gives the contracting officer a prompt notice in writing before disturbing the conditions (or secures an extension of the time for giving such notice) and asserts the claim before final payment of the contract. (b) Notice of differing site conditions. When a contractor believes that a differing site condition has been encountered, the clause requires that a prompt written notice be given to the contracting officer so that the condition of the site can be investigated, the facts can be ascertained, and a determination can be made regarding the presence or absence of a differing site condition. The prompt notice requirement enables the Government to examine the condition of the site and, if necessary, (1) to modify the contract so that it will reflect the increased or decreased cost of and time for performance or (2) to develop records concerning any increase or decrease in cost of and time for performance. Cost and time information is essential for an independent Government judgment regarding an equitable adjustment of the contract. A failure to give a timely notice could seriously prejudice the Government's ability to determine the extent to which the contractor or the Government is entitled to an equitable

adjustment. Since the existence of a differing site condition is not always recognizable immediately, the clause provides that the contracting officer may extend the time for the submission of the required notice. The purpose of the authority to extend the time for the notice is to ensure that contractors are not deprived of the remedy provided by the clause because of an inadvertent failure to give the required notice. However, this authority to extend the time for the notice does not entitle a contractor to a time extension beyond the time when he knew, or reasonably should have known, of the existence of a differing site condition. If the contractor gives the required notice at the time he knew, or reasonably should have known, of the existence of the differing site condition, he is entitled to an equitable adjustment which reflects the increased costs and time required for performance that result from the differing site condition. If the contractor fails to submit the required notice to the contracting officer by the time he knew, or reasonably should have known, of the existence of a differing site condition, he is not entitled to an equitable adjustment which reflects the increased costs and time required for performance prior to the time when he gave the notice or the time when the Government had actual notice of the existence of a differing site condition.

(c) Processing of claims. (1) Since the time required by the contractor to ascertain the amount of his claim varies with the circumstances, no specific time for submission of a claim is specified in the clause or in this section. The clause simply states that no claim will be allowed if asserted after final payment. However, contractors should not unnecessarily postpone the submission of claims for equitable adjustment. (2) To prevent contractors from unnecessarily postponing the submission of claims, contracting officer shall take the following actions:

(i) When a contractor gives a prompt written notice of a differing site condition but has not submitted a claim for an equitable adjustment, although there has been a reasonable opportunity to ascertain the amount of the adjustment involved, the contracting officer shall send a written request to the contractor (by registered or certified mail) that he submit within a specified period of time either a written claim or a request for an extension of the time for submission of the claim together with the reasons why the additional time is needed.

(ii) In the event that the contractor fails to submit a claim within the time specified in the request, or an approved time extension, the contracting officer shall make a unilateral determination of the amount of the equitable adjustment which the contractor is entitled to and shall notify the contractor of the determination. Such unilateral determination may not be appealed under the Disputes clause of the contract.