According to Vicki's Card Making Ideas, the first consideration regarding what to write in an anniversary card is who the card is for. A card that is for a significant other will be different than a card that is for a business partner. Vicki's Card Making Ideas suggests that you can start by saying thank you for the past year. Go on to mention certain events that have happened over the past year that mean a lot to both of you.
"Thank you for another wonderful year" is a short and simple phrase that can go into an anniversary card. This phrase would be best used in giving an anniversary card to a business partner or other associate because it is not romantic in nature. It is a simple phrase that allows you to show appreciation without crossing over any boundaries that you wish to maintain as a professional.
Placing a phrase about love in an anniversary card is appropriate if the card is for your partner. Examples suggested by Vicki's Card Making Ideas include "My love for you grows and grows with each passing year" or " Anniversaries pass quickly, but our love will always stay."
For a Friend
The key to writing something nice in an anniversary card for friends is to find a phrase that will appeal to both partners. Examples suggested by Vicki's Card Making Ideas are "To a wonderful couple, wishing you another year of happiness", "May this anniversary reflect all the special moments you've shared, and all the wonderful moments to come", and "Just as fine wine improves with age, may your love for each other do the same."