I am trying to figure out how to estimate quarterly tax payments. After some wonderful help on this forum, it seems I'll need to do this for my state, but not for the federal government.
From what I understand, estimated adjusted gross income requires that I include estimates for dividends and capital gains. How do I do this when filling out quarterly tax estimates since I don't know those values in advance? Those values tend to fluctuate a lot. Should I just use my expected wages for my estimated AGI and leave the rest out?
Also, for tax to be withheld, how, again, do I estimate those values? I can do so for my own wages, but my wife is on an income (not salaried) so her pay varies. (She might have a salaried job later in the year, but we don't know yet.) Should we overestimate our expected AGI and underestimate our expected withholdings when filing jointly? Is there any penalty for doing so i.e. erring on the side of caution?