It might also be reduced...if you buy a Muni bond during the year, and you pay, and report, the accrued interest you paid out to buy that Muni, and $$ reported on a 1099-INT. (not a problem for Bond funds reported on 1099-DIV though...they take care of it in the background)
If you are ever in that particular situation for a 1099-INT, and the 1099-INT has entries in boxes 1, or 3, in addition to box 8.....if that happens you must take out the box8 & 13 $$ amounts and report them on their own 1099-INT before you apply the accrued interest you paid on the page that follows the main form.
If you don't, then the accrued interest you paid out, gets proportioned (improperly) among the values in boxes 1, 3, & 8
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
