Square quotes mine. This should be standard practice for all tax filers using an online tool or downloadable application. In most cases you, as the taxed citizen, will be held liable for any mistakes on your return. Very few situations will find the tax software provider being legally at fault for an incorrect calculation. Protect your own ass(ets) by verifying your input with separate providers. If there any discrepancies, figure out why and file with the correct result. Do not try to "get away with" filing with the provider that is most in your favor without understanding the reason; from the point of view of your government, you might be filing a fraudulent tax return. Willful negligence of tax law is not a valid excuse in their eyes.