I'm not sure if I'm following you but I think I'm having the same predicament. In my case I must give some space to the ADBannerView at the top of the screen so what I did was in the viewDidLoad method I added:

[self.tableView setContentInset:UIEdgeInsetsMake(50,0,0,0)];

the values it takes are UIEdgeInsetsMake(top,left,bottom,right).

Alternatively the same with Swift:

self.tableView.contentInset = UIEdgeInsetsMake(50, 0, 0, 0)

Swift 4.2:

self.tableView.contentInset = UIEdgeInsets(top: 50, left: 0, bottom: 0, right: 0)

Swift 5.1

add the following in viewDidLoad

tableView.contentInset.top = 100

Really that's all there is to it.

override func viewDidLoad() {    super.viewDidLoad()    tableView.contentInset.top = 100}

You can add an "empty" header view to the table... this would give the initial appearance of the table to have an offset, but once you started scrolling the offset would be gone. NOt sure that's what you want.

If you need a permanent offset and are not already using section headers, then you could create the offset similarly to above by making custom views for the section headers, especially if you just have one section, this could give you the look of a permanent offset.

I can post sample code if it sounds like either of those are what you are looking for.