I must admit, I don't fully understand admin boundaries/levels. I just used this value (6) based on other nearby islands,as being tagged as a boundary but with no level was flagged as an error.

After looking into it, I found a map (https://portal.spatial.nsw.gov.au/portal/home/webmap/viewer.html?useExisting=1&layers=3e1edb6861524b5490c74db81e42433a) that shows Wasp Island as separate to the LGA of the mainland. Does that mean it's unincorporated, and if so, is level 6 then correct?

Thanks, I didn't know about the addresses on the base map. I'll make sure to use that in future.

Didn't see a validation error upon upload (they normally popup and I fix them), but fixed it now nevertheless.

I've been using DCS Base Map for tracing/aligning buildings, and then SIX Maps for confirming the address for each building (since I was told that's the canonical source for street addresses in NSW). Street addresses can't be copyright can they?

Oops, thanks for picking that up. Fixed.