A handwritten note of thanks holds tremendous loyalty-building power among customers and clients, but it can sometimes be an overlooked detail. To help event planners, vendors, and companies make a lasting impression and grow their relationships, here are business-appropriate thank-you cards—just in time to show some love on Valentine's Day.

A smile's in the mail with the whimsical card from Tiny Prints' business collection. The greeting features a short but sweet "thx" message on the inside, and can be customized with a company name. Pricing starts at $43.50 for 25 cards (white envelopes included).
Photo: Courtesy of Tiny Prints

Texting goes old school with the printed flat card decorated with bright chat bubbles from Tiny Prints. Pricing starts at $29.75 for 25 cards (white envelopes included).
Photo: Courtesy of Tiny Prints

The delicate greeting from Crane & Company features "merci beaucoup" written in red, along with a matching envelope with black polka dots. A box of 10 cards costs $17.
Photo: Courtesy of Crane & Company

Customizable photo cards from Luxe Cards can showcase images from events, catering, or staff members, along with a company logo and other embellishments, for a memorable impression. Pricing starts at $1.21 each with a minimum order of five cards; envelopes are available for an additional fee.
Photo: Courtesy of Luxe Cards

The flat black-and-white card from Gartner Studios Inc. features a spot for a business card, plus a blank space for a message. A pack of 20 costs $9.99.
Photo: Courtesy of Gartner Studios, Inc.

Ideal for eco-friendly, sustainable businesses, ForeverFiances' thank-you notes are made from recycled paper that's embedded with wildflower or garden herb seeds. Recipients can plant the customizable cards and watch them grow. Pricing starts at $133.30 for 30 cards (blank envelopes included).
Photo: Courtesy of greenbusinessprint.com

Customers will feel the business love with the big, bold-lettered "Valentine" from CroninCards. A box of 10 cards with red envelopes costs $12.50.
Photo: Courtesy of CroninCards

Suitable for summer events, the ice cream cone card from CardsDirect screams customer appreciation and can include a custom greeting inside. Pricing starts at $46 for 15 cards (mailing envelopes included).
Photo: Courtesy of CardsDirect

Crane & Company's engraved hashtag correspondence cards will help any company start trending. The cards are paired with gold foil-striped envelope liners. A box of 10 cards costs $19.
Photo: Courtesy of Crane & Company

The Piet Mondrian-inspired card with vibrant color blocks from CardsDirect would fit well in the desks of event designers and planners. Pricing starts at $45 for 15 cards (mailing envelopes included).
Photo: Courtesy of CardsDirect

The customizable chalkboard-style card from Luxe Cards acknowledges patrons who offer business referrals for the kind (sometimes forgotten) gesture and thanks them for their support. Pricing starts $2.57 each with a minimum order of five cards; envelopes are available for an additional fee.
Photo: Courtesy of Luxe Cards

The retro "businessman" thank-you cards printed on heavyweight textured paper from CroninCards add a touch of nostalgia to correspondence. A box of 10 cards with envelopes costs $12.50.
Photo: Courtesy of CroninCards

A cheery saying can help end an event on a sweet note with teams, clients, or vendors; the card from CardsDirect can feature a custom verse and personalization inside. Pricing starts at $28 for 10 cards (mailing envelopes included).
Photo: Courtesy of CardsDirect

The carnival-inspired, candy-striped flat card, designed by Wiley Valentine for Tiny Prints, offers the perfect ending to a circus-theme event. Pricing starts at $29.75 for 25 cards (white envelopes included) and is available with blue or orange striping.
Photo: Courtesy of Tiny Prints