Box 1a and box 1b are one figure and a slice of it. Box 1a, "total ordinary dividends", is the gross amount, and it includes the qualified dividends shown separately in box 1b. That relationship, and what makes a dividend qualified in the first place, are owned by the ordinary dividend and qualified dividend pages. What is worth adding here is what else the instructions require to be inside box 1a: dividends from money market funds, net short-term capital gains distributed by mutual funds, reinvested dividends and section 404(k) dividends paid directly from an employer corporation. A fund's short-term gains never appear as capital gain on this form, because distributing them converts them into ordinary dividends.
Boxes 2a through 2f are the capital gain family. Box 2a is the total capital gain distribution, which is always long-term whatever your own holding period, and which goes to Schedule D rather than to the dividend line. That is the capital gains distribution page's subject. Boxes 2b, 2c and 2d break out the slices taxed under their own rules: unrecaptured section 1250 gain, which carries a 25% rate ceiling; section 1202 gain from qualified small business stock; and collectibles gain, which carries a 28% rate ceiling. Boxes 2e and 2f are section 897 amounts and, as the instructions say, do not need to be completed for recipients who are US individuals.
Box 3 is the box people misread as free money. A nondividend distribution is a payment that exceeded the payer's earnings and profits, so it is legally a return of your own capital rather than a share of profit. It is not taxable when received, and it reduces your basis in the shares by the same amount. Once basis reaches zero, further nondividend distributions are capital gain. The consequence arrives later and in a different place: a smaller basis means a larger gain on sale. Brokers frequently reclassify part of a REIT's or a fund's distributions into this box in February, which is one of the ordinary reasons a corrected Form 1099-DIV arrives after a return has been filed.
Box 5 exists for one deduction. Section 199A dividends are qualified REIT dividends and the equivalent amounts paid by a regulated investment company, and the instructions confirm that this amount is also included in box 1a. It is reported separately because it is eligible for the qualified business income deduction, so it is subtracted out of the ordinary pile for that one purpose and left in it for every other.
Boxes 12 and 13 carry tax-exempt income through a fund. Box 12 is exempt-interest dividends, meaning municipal bond interest earned inside a fund and passed through to shareholders. It is generally excluded from federal gross income and is still reported, and it still matters on a return: it feeds the provisional income calculation that decides how much of a Social Security benefit is taxable, and it appears on Form 1040. Box 13 is the slice of box 12 attributable to specified private activity bonds, which is an alternative minimum tax item. Note that a fund pays exempt-interest dividends on Form 1099-DIV, while a bond you own directly pays tax-exempt interest reported in box 8 of Form 1099-INT.
The remaining boxes. Box 4 is federal income tax withheld, which here means backup withholding. Box 6 is investment expenses, which the instructions say is also included in box 1a. Boxes 7 and 8 report foreign tax paid and the country it went to, which is the input to the foreign tax credit. Boxes 9 and 10 are cash and noncash liquidation distributions, and the instructions caution that these apply only to corporations in partial or complete liquidation and must not also appear in box 1a. Box 11 is a FATCA reporting checkbox.
Two things that look like dividends and are reported elsewhere. The instructions carry an explicit caution: amounts commonly called dividends on deposit or share accounts at cooperative banks, credit unions, and domestic and federal savings and loan associations are legally interest, and they belong on Form 1099-INT. Separately, taxable dividend distributions from life insurance contracts and employee stock ownership plans go on Form 1099-R, and substitute payments in lieu of dividends, which arise when a broker lends out your shares, go on Form 1099-MISC. That last one is worth knowing because a substitute payment looks identical in an account and is never a qualified dividend.
Some recipients never get one. No Form 1099-DIV is required for payments to a corporation, a tax-exempt organization, an individual retirement arrangement, an Archer medical savings account, a health savings account, a US agency, a state, the District of Columbia, a US territory, or a registered securities or commodities dealer. This is why dividends inside a retirement account generate no form: not because they are invisible, but because the account is an exempt recipient.