I have previously posted on the issue of amendments to permits. I have recently come across the case of Groenan v Casey CC  VCAT 1822, which contains a discussion regarding the issue of retrospective planning permit applications and intensification of use. Although the case relates to dog breeding, the concepts discussed in the case are of wider application.
A retrospective planning permit application is one that is made when a “use” has commenced or has been intensified without the appropriate permission.
In this proceeding the Applicants were seeking to amend their planning permit to intensify the animal husbandry occurring on the site. The Applicants had a planning permit to keep 30 dogs on the subject site and were seeking to increase this to 50. The increase in the number of dogs also required building works.
Council refused the application on grounds which included the failure to provide adequate information to accompany the application. The Tribunal made the following finding on this point:
I consider that under normal circumstances the lack of information submitted with the application would be sufficient reason to disallow the application for amending the permit, particularly if the level of policy support for the use of dog breeding/boarding was not strong for this location. However, I note that Council has erected roadside signs stating that this area is identified as an intensive use area for dog breeding. It can be seen therefore that the area is already devoted very largely to dog breeding /boarding and this is likely to continue and expand in the future. Accordingly, I am not persuaded to disallow the application on the basis of a lack of information in this instance. 
In its reasons the Tribunal also considers the issues that arise with intensification of animal husbandry including, waste management, water management, noise and shelter. The Tribunal also discusses the Code of Practice for the Operation of Breeding and Rearing Establishments. Ultimately, the Tribunal finds that the intensification will not result in unacceptable outcomes and that the amendment to the planning permit is appropriate.
However, readers should note the warning that appears at the end of the Tribunal’s reasons with respect to the issue of retrospective planning permit applications.
I also want to make it clear to the landowners that it is noted that this is the second time the matter of dog breeding activity on this site has come before the Tribunal seeking retrospective approval for use and development that has already occurred and commenced. This is not appropriate and the landowners should take note that undertaking changes to the approved use and development without first seeking appropriate approvals from Council is unlawful. I strongly advise the landowners to ensure that they make the necessary enquiries with Council before they make any further changes to how their dog breeding business operates in the future. 
Be aware. You should always check carefully that you are complying with the conditions contained in a planning permit. If in doubt seek advice. Retrospective applications are inherently risky as they could result in a refusal or alternatively conditions that are costly to comply with. Further, Council’s could also commence enforcement applications.