A notehead in the space just past the staff or just past an existing ledger line gets no line of its own

Ledger lines are drawn only at LINE-levels beyond the staff (spaced a third apart, i.e. 2 diatonic steps), never at the intervening SPACE-levels. A notehead that lands in the first space beyond the staff edge, or in the space between two already-drawn ledger lines, needs no additional line stroke of its own — it reads by simple proximity to the nearest already-visible reference line (the staff's own edge line, or the last ledger line drawn for a note further out). This falls directly out of the count formula in ledger-line-count-formula (floor(steps/2) is unchanged between a space-note and the line-note just below it), and is the precise meaning of what several older texts call the 'partial ledger line' case.

A renderer that draws a short stub or partial tick for every space-level note beyond the staff (over-drawing), or conversely omits the necessary line for a note that IS on a line-level (under-drawing) — both are the same bug in the floor(steps/2) formula, just off by a rounding direction.

Gould, Behind Bars, and Read, Music Notation ch.1, both describe ledger lines as continuing the staff's line/space alternation, which implies (without both authors stating it as a separate named rule) that space-notes beyond the staff get no line of their own. Ross, The Art of Music Engraving, is the more explicit of the four on this specific point, describing the 'in-between' note as requiring no extra mark beyond what the adjacent line-note already established.

This rule needs the notated content and the rendered result together — the score says what should happen, the page says whether it did.