Financial incentive interventions for promoting smoking cessation are complex, but effective. We conducted workshops with 59 community members and Stop Smoking Professionals (SSPs) to co-design a pilot financial incentive intervention for smoking cessation targeting disadvantaged communities in Ireland. Following contributions from 27 participants (mostly SSPs), we qualitatively examined perceived facilitators and barriers to implementation. Results aligned with 8 out of 14 domains of the Theoretical Domains Framework (TDF) - a validated framework to understand implementation determinants of health behaviour change. Example facilitators included: establishing clear guidelines, providing staff training, appropriate targeting for public defensibility. Example barriers included: an inability to account for all potential challenges, disruption to work dynamics if training is insufficient, biological-testing concerns, public disapproval, limited technology. Eligibility precision, staff role clarity, objective cessation verification and media management were particularly salient. Identifying perceived facilitators and barriers aligned to theory allows for more specific strategies for design and implementation.