I noticed that when I entered my T4/Releve1 data for myself, it affects my wife's tax refund, and vice versa. If I delete my T4/Releve1, her balance due reduce. But why?

The Refund calculator in the upper left hand corner of Turbo Tax is a dynamic live calculation based on the tax information as you supply it.

In the circumstance you have experienced the software was reviewing your return and your spouse at the same time. As you provide your income the software considers potential tax deductions and credits. With only your T4 entered and no income as yet provided for your spouse the claim for Spousal Amount was considered within the refund calculation.

Once you add your spouse’s actual income the software will then recalculate based on the additional information and disqualification of certain deductions. The final bottom line number can only be ascertained once all of the pertinent information has been imputed.

Review the detailed tax summary to verify that all amounts are reported correctly.

You can find a detailed summary of your tax return under the "Review" tab > "Bottom Line (tax summaries)"> then look for the paper and magnifying icon in the lower left hand corner, select "Detailed Tax Summary". You will have a line by line sample of the Federal Tax Return.