Approval for outdoor staircase

We’ve discovered that our recently purchased property has renovations that weren’t approved by council. The plans held by council date back to the 1980s and the current structure is very different to what was approved in those plans, but there are no other more recent development approvals. We want to build an external staircase from an existing first floor deck into the backyard. The problem is that the 1980s plans had a smaller deck in a different spot, with stairs down to the yard. If we apply for council approval to now build the staircase, will we just create a nightmare of problems with council?