(b) RIOC shall have 15 calendar days after receipt of an invoice at the designated payment office to notify the contractor of:

1. (1) defects in the delivered goods, property or services;
2. (2) defects in the invoice;

3. (3) suspected improprieties of any kind.

   The existence of a defect or impropriety shall prevent the commencement of the 30-day period specified in subdivision (a) of this section, provided that RIOC notifies the contractor of the defects or improprieties within 15 calendar days of receipt of the invoice. If such notification is not given within 15 days, the number of days allowed for payment once the defect or impropriety is cured will be reduced by the number of days between the 15th day and the day notification was given to the contractor. If RIOC fails to provide reasonable grounds for its contention that a defect or impropriety exists, the date by which contract payment must be made in order for RIOC not to become liable for interest payments shall be calculated from the date of receipt of an invoice.

(c) RIOC may justify extension of the contract payment date in order for RIOC not to become liable for interest payments in accordance with section 4502.6 of this Part. The bases for extension may include, but shall not be limited to, the following when:

1. (1) in accordance with specific statutory or contractual provisions, payment must be preceded by an inspection period or by an audit to determine the resources applied or used by a contractor in fulfilling the terms of the contract;
2. (2) the necessary State government appropriation required to authorize payment has yet to be enacted;
3. (3) a proper invoice must be examined by the Federal government prior to payment; and
4. (4) such date by which contract payment must be made is modified in accordance with this subdivision.