regarding the benefit of rent as an expense - Everyone gets a standard income exemption of 85,000 and a standard deduction of 90,000. You can use your rent expense to replace the 90K standard deduction in addition to other itemized deductions (pg 52 of the Taiwan tax booklet). So if your yearly rent is higher than 90K or if you have other deductions then it is a benefit to you. It is a little unclear however if you might get your landlord in trouble if you claim rent as a deduction. Some (or many) landlords don't claim rental income as income and I think the tax office will contact your landlord about this income and expect them to pay taxes. You aren't doing anything wrong but this could cause poor relations between you and the landlord and either your rent will go up or you won't be able to renew your lease. Just a word of caution.
In addition to the 85,000 and the 90,000 you also get a 128,000 salary/wages deduction. Overall it is about 300K of non-taxable income for a single tax filer with no dependents.
The benefit of your parents being dependent on you is an additional 85,000 of non taxable income (age 60-70) or 127,000 (age 70+) per parent. That is a refund of 10-15,000/parent if you are in the 12% tax bracket. I do not know what documentation is needed to claim them as dependents since I do not do this. My parents are 60 and 62 now but I would feel a little conflicted about claiming them since I don't support them financially at all. Perhaps later on but both still work. This was one thing that came up in an off topic conversation while I was recently at home. Health insurance (US) is still way too expensive for them until they reach age 67 (Medicare) for them to not work (I didn't ask any questions nor will I offer advice).
You get your money back the following August after you file your taxes. So for the 2015 income taxes you get your refund in August 2016.
ilikecoffee listed all of the possible deductions but those are only if your company provides you with something like housing. The deductions from your paycheck should only be for income taxes, NHI (around <1000NT if you earn 60,000/mo), and labor insurance (a little more than NHI I think). Pension (and the deduction for it) is only available to those that are married to a Taiwanese spouse AFAIK.
The numbers above are from the 2015 tax booklet. All deductions have increased a little this year but I don't have that booklet linked yet.https://www.pwc.tw/en/publications/asse ... k-2015.pdf