Kate Cassidy Honors Late Boyfriend Liam Payne on Birthday

9:20 AM PT -- Kate Cassidy followed up her video montage for Liam Payne's birthday with a long, poignant note posted to Instagram.

In the upload, in which she shared several past photos from their time together, KC declared she would "give up years in [her] life to give [him] a few more."

Kate Cassidy is sharing a glimpse into her love story with Liam Payne ... uploading a sweet tribute on what would've been the singer's 32nd birthday.

The TikTok star shared a video montage Friday on Instagram of candid moments of herself and Liam enjoying everything from adventures abroad, to meals together, to other intimate moments.

KC said the tribute was meant to commemorate "a special day for a special soul," noting just how much she missed her former flame.

She added ... "Happy Birthday Liam. I wish we could celebrate together. In the next life I guess❤️"

This isn't the first time Kate has opened up about her heartbreak in the aftermath of Liam's death. Remember, Kate had been with Liam in Argentina in the days leading up to his death in October ... she and Liam attended 1D alum Niall Horan's show in Buenos Aires at the Movistar Arena earlier that month.

Kate chose to leave their vacation early on her own, however, after LP extended the trip's length.

Tragedy struck days later ... when the One Direction alum fell to his death from the balcony of his room at the CasaSur hotel. Toxicology reports later showed the singer had alcohol and drugs in his system ... with 5 people then being arrested in connection with his passing.

Liam had battled addiction before to his death, revealing in May 2023 he'd completed rehab and was 100 days sober.