I'm Australian and live in Vietnam with my Vietnamese Wife.
The Vietnamese rule of 183 days making me liable to pay tax in Vietnam was a worry, so before I finished working in Australia, I fully researched everything I could and still relied on Tax Consultants to advise me, however, my (our) situations are all different and I couldn't find an expert and relied solely on the Australian Taxation Office for information - and they could only provide incorrect info or very limited info (and that limited info was from deputy tax commissioners).
I didn't want to pay no tax, only wanting to follow the rules and pay whatever I needed to.
I read the Duel Tax Treaty (also known as Agreement and some other names) and the different names and the way it was referred to was my first warning. Gov't documents are like Gov't contracts that I've read, poorly written.
All the Duel Tax Treaties I read were very similar, which makes sense and they try and maintain some commonsense - strange coming from Gov't . But easy to read and easy to translate.......
I read the Price Waterhouse and Cooper tax booklet for expats in Vietnam which is released each year on the internet and sent emails to both PWC and Deloit accountants asking if I would have to pay tax on my Super and bank interest in Vietnam. I also sent my sister-in-law to ask her Vietnamese Gov't contacts in taxation the same question and both answers were no.
The Duel Tax Treaty stated that I paid tax on Super (Private superannuation pension) in the country I was resident and I pay tax on my bank interest in the country it was in. That meant I paid tax at 10% on my bank interest to Australia for tax. If I sent my money to a Vietnamese Bank, I could get a better interest rate and pay no tax, however, don't wish to have all my assets in one country. I got rid of Shares a long time ago and had only one house left in Australia at the time I started researching. And I was always going to sell the last house, which I did before the Private Ruling was conducted. Lucky it was beneficial to cull my investments to make life very easy. After speaking to the Australian Tax Office, I also arranged for a Private Ruling from them which consisted them asking me questions via email regarding my circumstances. My Private Ruling is in place for 5 yrs, 2 yrs left on it and then I apply for another one. Note it wasn't mandatory to have a Private Ruling but it has helped because Taxation Staff in Australia have major problems, takes 5 mths to do my tax each year.
Because I do not work here, I am not a resident of Vietnam except for the 183 days rule which in Vietnamese Tax Law, means I am a resident for Tax Purposes. My Private Ruling in Australia states I am a non resident of Australia for tax purposes only, because I live in Vietnam for more than 183 days, making me liable to pay tax and therefore covers me on the Tax Treaty.
I provided no documents from Vietnam (since I wasn't liable to pay them tax, they were not interested) and only provided documents and statements from the Tax Treaty and PWC Tax Booklet for expats in Vietnam and Vietnamese tax Laws from the internet.
The commonsense rule is that if properties and shares are in another country - that is where you pay tax. This is to stop people using other countries to not pay tax and since laws in paying tax can be so complicated with each country having different laws regarding it, that it would take too much time on each individual's yearly tax assessment which would hold up Staff in a Tax Office for too long.
Everything should be written in the Tax Treaty.