If you decide to update a completed review that has a PROSPERO record, you can access this by signing in and going to My PROSPERO records. You can make changes to the protocol and submit it as an update and it will be processed as for a new review.
It can be difficult to decide whether an update to a review is in fact a new review. There is little published guidance on this. PROSPERO adopts a pragmatic approach. If changes to the review questions or methods are so substantial that they require major changes to the original protocol, this should be regarded as a new review rather than an update.
Examples that would constitute a new review:
If in doubt, a new record should be created. This will minimise the complexity of the editing to the original record in PROSPERO and make it easier for users to distinguish between the original review and the later version. Links between the new and original review can be added in the registration form.