領収書, りょうしゅうしょ
simplified receipt with a blank line to be filled out with the customer's name (used specifically for claiming expenses), hand-written receipt
領収書は必ず保管してください。
が
Particle
1. indicates sentence subject (occasionally object)
2. indicates possessive (esp. in literary expressions)
Conjunction
3. but, however, still, and
after the volitional form of a verb
4. regardless of, whether (or not)