Not all taxes are necessarily unjust–and paying taxes is a citizen’s duty. In the Shariah, the government can levy taxes if zakat and other Shariah-taxes are not sufficient to fulfill recognized public needs.
It is not permitted to cheat and deceive the government in regards to taxes. However, one can take all legal means to minimize one s taxes. The Messenger of Allah (peace and blessings be upon him) said, “I was only sent to perfect noble character.” [Ahmad, and others] He (Allah bless him and give him peace) said, “The one who cheats is not of us.” [Muslim, Tirmidhi, Abu Dawud, and others] He (Allah bless him and give him peace) also said, “The one who does not fulfill trusts has no faith, and the one who does not fulfill commitments has no religion.” [Ahmad, with a sound chain of narrators]
And Allah alone gives success.