The tax year runs from Jan 1 to Dec 31.
There are essentially two categories of tax status for aliens (i.e. ETs...English Teachers). These are based on how long you have been in the country for a given tax year.
Category A - 0 to 183 days - You must pay 20% tax on your income. You cannot claim deductions.
Category B - 183 days or more - You will be taxed according to the following progressive scheme:
|total income for the year||your income tax rate|
|0 to 370,000 nt||6%|
|370,001 to 990,000 nt||13%|
|990001 to 1980000 nt||21%|
If you fall into Category B you can also claim a NT$72,000 exemption for each taxpayer, spouse and dependent in your family. There is also a standard NT$43,000 deduction for each individual or a NT$65,000 deduction for each married couple.
Your status in category B will carry over to the next tax year even if you don't stay in the country 183 days the following year.
Analysis - You should get here in the first half of the year so you fall into category B. Please note however that you generally do not get 'on the books' for a month or more (often quite a bit more). Thus if you arrive in September, you may only begin paying 20% tax on income in November. Thus your income tax will not be too onerous. There are also deductions that the schools often claims for you, further lowering your declared income and total tax. Generally speaking, the tax situation here is excellent.
For more information from Taiwan's Tax Bureau click here.