Is customer consent needed?

No, you do not need your clients' consent because the application is used to perform a contract/deliver a service. Of course, you need to inform your clients in your privacy notice that some of their data might be transmitted to third parties. As a data controller, you need to verify if your software provider implemented compliance with GDPR requirements and avoiding using not trustworthy software.

Here you can find some articles about privacy policy and consent:Everything you need to know about the GDPR Privacy Notice: https://advisera.com/articles/gdpr-privacy-notice-6-key-elements-to-include/Is consent needed? Six legal bases to process data according to GDPR: https://advisera.com/eugdpracademy/knowledgebase/is-consent-needed-six-legal-bases-to-process-data-according-to-gdpr/

EU GDPR document template Privacy Notice: https://advisera.com/eugdpracademy/documentation/privacy-notice/

You may also consider enrolling in this online EU GDPR Foundations Course: https://advisera.com/training/eu-gdpr-foundations-course//

thanks a lot for your replay. that was helpful. Kind Regards, Elina