The phrase "a complimentary gift" is correct and usable in written English.
It can be used to describe a gift that is given free of charge, often as a gesture of goodwill or appreciation.
Example: "As a token of our gratitude, we would like to offer you a complimentary gift with your purchase."
Alternatives: "a free gift" or "a gift at no charge".
Guests who stay in this Zen-styled retreat receive a complimentary gift of polished blue quartz.
More immediate perks include a complimentary gift certificate for Mercedes merchandise and award points for gasoline purchases.
Martin, Sally, and Tony went to Antey's department store with Swirsky to see the Christmas Grotto and get a complimentary gift.
This luxury building is the first to partner with Baroo, a concierge pet service that offers in-home vet visits, pet coaches, catering (to meet your pet's custom dietary needs), walkers, groomers, sitters and a complimentary gift basket upon move-in.
Presenters and performers at this year's Oscars can be expected to be handsomely rewarded for their trouble with a complimentary gift package thought to be worth up to $100,000 £65,7333).
Mothers will receive a complimentary gift bag.
Included are a deluxe room, complimentary gift wrapping and complimentary valet parking.
The donkey is about two inches long and gold-tone, and is wearing a top hat and a jewelled saddle blanket and a little tag saying "complimentary gift — not for resale".
Alternatively, there is the use of an exclusive golf course and the complimentary gift of a shotgun (it's all been arranged in advance with customs so you can take it past airport security on the way home) or perfume-making sessions.
I later found out that she only bought it so that she could receive the complimentary gift: a Taj-Mahal scale vanity with 6 lipsticks, 12 eyeshadows, blushes, brushes and a fold-down mirror.
Complimentary gift of a pair of Havaianas is a nice touch.
