When can I Amend the Claims in Japan?

The applicant can amend the claims at any time before an Office Action is issued.
The amendment restrictions are as follows:

• Addition of new matter is prohibited.

After an Office Action has been issued, amendments can only be made within the following timeframes:

• The response period to the Office Action
• The same time as the filing of an appeal to a Decision of Rejection

The amendment restrictions are as follows:

• In response to a non-final Office Action: addition of new matter and shift amendments are prohibited.
• In response to a final Office Action: addition of new matter and shift amendments are prohibited and amendments are limited to specific purposes.
• At the same time as an appeal: the same as for a response to a final Office Action.

After allowance, the applicant can make corrections, i.e., post-grant amendments, to the claims.
Corrections (post-grant amendments) will be explained in another article.

Details for each factor will be covered in separate articles.