How many letters does the top answer for “that may not be returned” have?

The most common answer is nonreturnable (13 letters).

Crossword clue: that may not be returned

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

nonreturnable 13 letters wn-def

that may not be returned

not to be returned. 67% similar → irreturnable

that may be returned 67% similar → returnable

not returned in kind 50% similar → unanswered, unrequited