Yes, it would be wrong for you to do this–whether anyone finds out about it or not. When you cheat on your taxes, you're stealing money from your government–and ultimately from those it helps. The Bible is clear: "You shall not steal" (Exodus 20:15).
The Roman Emperor was despised by most Jews in Jesus' time because his armies had occupied their nation. When Jesus was asked if it was lawful to pay taxes to Caesar, however, He replied that it was not only lawful but necessary–even if the Roman government was less than perfect. He said, "Give to Caesar what is Caesar's" (Matthew 22:21). The Bible also says, "Give everyone what you owe him: If you owe taxes, pay taxes; if revenue, then revenue" (Romans 13:7).
Your question, however, suggests that something deeper than money is at stake here–and that is your personal relationship to God. What (or who) has first place in your life? Is it money–or is it God?
Only you can answer that question–but I pray you will, frankly and honestly. Jesus warned, "You cannot serve both God and Money" (Luke 16:13). Never forget: Christ gave His life for you by dying on the cross for your salvation. Should you give Him anything less?
Follow the Steps to Peace online to learn about Jesus or recommit your life to Him.