During the search and examination stage of an international application, if the International Searching Authority (ISA) determines that the international application lacks unity of invention, the examiner will notify the applicant and issue the Invitation to Pay Additional Fees which indicates the number of additional inventions and fee per additional invention and the total amount that should be paid.

If the applicant doesn’t pay the additional search fees timely after receiving the said Notification, the ISA will conduct the examination based on the invention first mentioned in the claims.

In the international preliminary examination stage, if the examiner agrees with the decision of the ISA, and believes that the inventions lack unity, the International Preliminary Examining Authority (IPEA) normally will not make any examination for the inventions which have not been searched.

So what would happen to the above application in the Chinese national phase? 

According to the provision of the Implementing Regulations of The Patent Law and the Guideline for patent Examination in China:

Rule 115 Where, in the international phase, some parts of the international application have not been the subject of international search or international preliminary examination because the International Searching Authority or the International Preliminary Examination Authority considers that the international application does not comply with the requirement of unity of invention prescribed in the Patent Cooperation Treaty, and the applicant fails to pay the additional fee, whereas at the time of going through the formalities for entering the Chinese national phase, the applicant requests that the said parts be the basis of examination, the patent administration department under the State Council, finding that the decision concerning unity of invention made by the International Searching Authority or the International Preliminary Examination Authority is justified, shall notify the applicant to pay the restoration fee for unity of invention within the specified time limit. Where the fee is not paid or not paid in full at the expiration of the prescribed time limit, those parts of the international application which have not been searched or have not been the subject of international preliminary examination shall be deemed to be withdrawn.

Where, after examination, it is confirmed that the decision made by the International Authority is correct, the examiner will issue the Notification to Pay Restoration Fee for Unity to notify the applicant that, after examination, the decision made by International Searching Authority or International Preliminary Examining Authority is correct, and the applicant shall pay the restoration fee for unity or file a statement within two months; if the applicant agrees to the decision made by International Searching Authority or International Preliminary Examining Authority and fails to pay the restoration fee for unity, the applicant shall file an amended text that deletes the part for which an international search or international preliminary examination has not been conducted; if the applicant fails to pay or pay in full the restoration fee for unity, and fails to delete the invention lacking unity, the part for which an international search or international preliminary examination has not been conducted in the PCT application shall be deemed to have been withdrawn.

After receiving the said Notification, the applicant can take the following actions:

(1) Pay restoration fee for unity: the examiner will continue with the examination of the application after the fee is paid, and probably issue the Notification to make divisional application, the applicant could file divisional application afterwards as normal applications;

(2) Pay restoration fee for unity, and amend the claims: the applicant may amend the application to avoid issuance of the Notification to make divisional application, and the amendments are not limited to deleting claims which are lack of unity, other amendments for overcoming the deficiency are also allowed, but the amendments should not go beyond the scope of the original application; 

(3) Write a response to argue that the inventions have unity, and the examiner will review the response and re-evaluated the unity of the inventions;

(4) Do not pay the said fee with/without delete the inventions which don’t have unity, and for which an international search has not been conducted, the applicant shall not request for divisional application(s).

Generally speaking, if the applicant pays the unity restoration fee within two months after receiving the said Notification, or submits a statement to prove the unity of the claims, he will continue to enjoy the rights of all the claims, i.e. he may file divisional application for the inventions which were deleted or deemed to be withdrawn.

If the applicant fails to pay the unity restoration fee, or does not delete the inventions that have not been searched by the International Bureau, and can’t prove the unity of the inventions, he is not allowed to file a divisional application afterwards. 

Assuming that the applicant deletes the claims that lack unity initially before the examination of the application (i.e., when filing the application or filing the examination request of within three months after receiving the Notification of Entering the Substantive Examination), the examiner will believe that the unity defect has been overcome, and the applicant has voluntarily given up the claims that do not have unity, and there is no need and no reason to issue the Notification to Pay Restoration Fee for Unity; if the applicant does not pay the restoration fee for unity voluntarily, the applicant will lose the opportunity to file a divisional application for this part of the claim eventually.

In summary, for the inventions which are not searched due to unity issues in the international phase, if the applicant wants to make voluntary amendments and submit a divisional application in the future, he may pay unity restoration fee initiatively after entering Chinese national phase.