Should my tax return change drastically after entering 1099-R for military retirement income?

[SteamTrain]

Sure...it's all taxable income that changes taxes owed....and if you are getting SS, it can change the % of SS that is being taxed.
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Unless you mean that your taxes increased by a LOT more than ~20% of the distribution.  an absolutely Huge change in taxes owed (close to or larger than the distribution) usually indicate that you mis-entered the distribution $$…….like 300,000.00 instead of 30,000.00.   Edit the 1099-R and re-check every field

[SweetieJean]

Any increase in income can also reduce or eliminate some deductions or credits.