144 THE LAW AFFECTING ENGINEEKS 



express approval of that which is already done, will not 

 enable the contractor to sue for payment (see Richardson v. 

 Mahon, 1879, 4 L. K. Ir. 486). The "progress certificate" 

 is sometimes termed a " certificate on account." In the 

 model conditions sanctioned by the Institute of Electrical 

 Engineers it is specially provided (see Form IIA., Cl. 84, 

 post) that no such certificate is to prejudice the rights of the 

 purchasers against the contractor, or relieve the contractor of 

 his obligations for the due performance of the contract. 



It is usual to make provision for progress certificates by 

 saying that the contractor shall be entitled, upon the certifi- 

 cates of the engineer, to payments by the employers, in 

 accordance with provisions to the following effect : 



(i.) As the works progress, 80 per cent, upon the contract value of the 

 work from time to time delivered or executed on the site to the satisfaction 

 of the engineer ; 



(ii.) The remaining 20 per cent, (usually termed the retention money) 

 in respect of each distinct section or part of the works as follows : 



(a) 10 per cent, at the expiration of one month after the employer takes 

 over the works, and 



(b) 10 per cent, at the expiration of nine months after the first 10 per 

 cent, becomes due under (a). 



Payments made under parag. (i.), supra, are made on 

 "progress certificates" (see 'Form IIA., Cl. 34, post). To 

 avoid any chance of misunderstanding as to the effect of 

 these documents, it is often wise to insert a clause providing 

 that the certificates given during the work shall not in any 

 way prejudice the employer in the final settlement of accounts, 

 in case it should appear that the contractor has been paid too 

 much. (See ibid., Cl. 36.) 



4. Form of progress certificate. The following is a simple 

 form of progress certificate : 



I hereby certify that of may be 



paid the sum of as a instalment on account of the 



contract for the above : 



Contract 



Estimated value of 



Extra work 



(Signed) [Engineer] Date Eeceived from 



the above-named sum. 

 (Signed) [Contractor.] 



