When I went to Australia last year, I read on a travel forum that an Australia visa can be used to enter Taiwan, but it needs to be valid and unused.
Once used, and you already returned to the Philippines, you can no longer use it to enter Taiwan.
So, I did a little research on this. I learned that Philippine passport holders could enter Taiwan visa-free, if you meet the following qualifications:
1. You must have a valid visa or permanent resident certificate issued by USA, Canada, Japan, UK, Australia, New Zealand, or Schengen Convention countries.
2. You have never been employed as a blue-collar worker in Taiwan.
You will need to register at the website (https://niaspeedy.immigration.gov.tw/nia_southeast/). After completion, a travel certificate will be issued. Make sure you print it immediately or save it as pdf file in your computer. You must present the travel certificate to the immigration officer upon arrival in Taiwan airport to immigration.
It is also stated on Taiwan Economic and Cultural Office in the Philippines that a single-entry visa becomes invalid once it has already been used. However, a single-entry visa might be acceptable for the purpose of immigration inspection to enter Taiwan if it meets the following conditions:
A. On the same continuing journey, the visa holder uses it to enter the visa issuing country prior to his/her arrival in Taiwan;
B. The visa holder will arrive in Taiwan before its expiration date.
The route I planned was PHL-KOR-JPN-TWN-PHL, and I only had a single entry Japan visa that time. Although it is clear to me that even if you have a single entry visa, it is still accepted as long as it is a continuing journey, and the visa is till within the validity date, I still verified the information to Taiwan Economic and Cultural Office in Manila.
I told them that I only have a single entry Japan visa and my route will be JPN then TWN and asked if that would be an issue. The lady I talked to said it is okay, as long as it is on a continuing journey, and that my visa has not expired yet.
If you have a multiple entry visa from the item 1 above, then you won’t need to worry about the one I encountered during my 3 Countries using 1 Visa travel.
Also, you do not need to go to Japan or other countries stated in item 1 above before going to Taiwan. If you have a valid visa from those countries, you can just print a travel certificate then go to Taiwan.
So to my readers who were asking me about their planned route of PHL-TWN-PHL, and hold a multiple entry Japan visa, or even a single entry Japan visa but still unused and still within the validity date, the answer is yes. You can definitely enter Taiwan using your valid visas.