引き換え券	15736	8.7%
引換券	164056	90.9%
引替え券	68	0.0%
引替券	602	0.3%

daijs:
https://dictionary.goo.ne.jp/word/引換券/
ひきかえ‐けん〔ひきかへ‐〕【引換券】

https://eow.alc.co.jp/search?q=引換券

voucher is my intuition, and it's quite prevalent on reverso:
https://context.reverso.net/translation/japanese-english/引換券
https://ejje.weblio.jp/content/voucher

Reordered kanji.

A quick google shows that this is often printed on the tickets themselves, and that may prompt the frequency of the condensed-kanji form.

IME also gives me the 3-symbol version first.

We didn't even have 引替券, which is more common than 引替え券 (68 examples vs. 164,056 for 引換券). Unless there is a pressing reason, it seems like [sK] is preferrable to two [rk] forms, given just how many かえる kanji can potentially pop up.

@@ -4,3 +3,0 @@
-<k_ele>
-<keb>引き換え券</keb>
-</k_ele>
@@ -12,0 +10,7 @@
+<keb>引き換え券</keb>
+</k_ele>
+<k_ele>
+<keb>引替券</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
+<k_ele>
@@ -13,0 +18 @@
+<ke_inf>&sK;</ke_inf>
@@ -24,0 +30 @@
+<gloss>voucher</gloss>