In five to ten sentences, what is the tax advice or tax remedy applicable? Please apply the laws of the Philippines.

Mia, a compensation income earner, filed her income tax return for the taxable year 2017 on March 30, 2018. On May 20, 2021, Mia received an assessment notice and letter of demand covering the taxable year 2017 but the postmark on the envelope shows April 10, 2021. Her return is not a false and fraudulent return. Can Mia raise the defense of prescription? Explain *