How to incorporate a company in Singapore?
What are some good email address validation npm libraries?
How do you sell SAAS products overseas and handle tax?
Yes, in your case you will most likely only have to pay taxes in the UK on Australian and American profits, unless you have physical operations in those countries that generate profit. On EU profits on the other hand, you have to deal with the maze of VAT for each customer. If you were to sell physical products, then it's different story.
Best Value vs Performance email hosting (custom domain)
Should I inform the user that its a paid service before or after he submits his email address.