In short, two things: (1) register your sole-trader or similar business entity for tax purposes, and (2) close the Apple contract for paid apps. If you have a decent app idea, do these things as soon as you start development. Apple require developers to show evidence they are registered for local tax before allowing them to sell apps on the app store.
In my case, I gained an Apple Developer account soon after I started so I could test apps on real devices, but deferred the above until part way through development, under-estimating the time it can take. In Australia, business names are registered by the Australian Business Names registry, and it’s also possible to register for tax at the same time. Accordingly to their site, it can take up to 28 days to finalise. However in my case it took much longer. After chasing them, the process was finalised just after 7 weeks. Kinda crazy and unacceptable in my opinion.
During this time I realised another gotcha. Apple does not allow you to test IAP (in-app purchases) during development without a closed paid app contract (setup within iTunes Connect). Of course, starting the Apple paid contract process can only start once you can show Apple a screenshot of your business name registration complete with tax registration. I completed the contract 4 weeks ago with the screenshot, and I’m still waiting for Apple to finalise the contract. In the meantime, I’ve essentially finished the app, but I’ve virtually lost interest to submit it due to the delay.
BTW Apple do not mention anywhere in iTunes how long the contract closing process takes. The only clue you get is the ‘contact us’ part which says you can contact them after 3 weeks has elapsed.
So in total it’s been 12 weeks to get operational, and I’ve still not submitted my app since I’ve not had a chance to test IAP properly. I’m pretty sure my situation is an exceptional case, and I understand why the business name/tax registration took so long, but no idea why about Apple. So this is why I suggest to get in early to finalise paperwork to not slow down your app-development momentum.