By default, a donor gets a year-end receipt when their Tax receipt preference is Consolidated annually and their gifts in the tax year (January 1 to December 31) that don't already have a receipt add up to at least the Minimum eligible total. Gifts that already have a receipt are left out, so no one is receipted twice.
Details
You can change the rules on the Year-end receipts screen before each run. Turn off Only donors set to an annual receipt to include per-gift donors too; donors set to Do not receipt are never included. You can also limit the run to one Fund. Gifts marked Not required or imported, gifts linked to an event, and archived contacts are left out. With Hold donors with no address on file on, donors with no mailing address are held until you add one.