This is an incredibly naive question but I can't seem to figure it out with Google. On United States tax forms you see boxes along the right side, but then there are often boxes just to the left of those in the center of the page, for example Box 8b and 23 on Form 1040. Is there some difference conveyed by the location of the boxes? I noticed that on the forms TurboTax filled out for me, some boxes in the center are not filled out even though I can't see any reason why they shouldn't be. Are boxes on the right required and those in the center optional or something?
Line 8b is there for you to report the amount of nontaxable interest (usually from municipal bonds) that you have received. The amount does not get included in the box on the right because it is not taxable. It used to be that this amount was not required to be listed in Form 1040 at all, but the law in this regard changed quite a while back. The IRS needs this information to figure out your Modified Adjusted Gross Income (MAGI) whose definition depends on what use the MAGI is to being put to. For example, those with high MAGI have to pay income tax on their Social Security income and those with high MAGI cannot make contributions to Roth IRAs, but MAGI is defined differently for these two applications.
The amount on Line 23 gets added up with the amounts on Lines 24-35 and the total is reported on Line 36.
Boxes on the right are not required to be filled (even with 0) if there is nothing to report on them.
The non-right boxes are intermediate calculations. If you look at your 1040 you linked, you'll see how 23-35 are just added to get to 36. The form was designed to help avoid confusion. The code is complex enough, written by congress. As enforcer, the IRS' job of compliance is to also attempt to reduce errors. Again, if 23-35 were right-aligned, there would be no math difference, but consider how it would look.
The rest of the form similarly offsets to the left where items are aggregated before entering. A glance at my final 1040 shows an easy flow, first page adding to Total Income, then ending with AGI, etc.