It's always a good idea to express your gratitude when receiving a job offer from an HR representative. Here's an example of how you could thank them:

Dear [HR representative's name],

I wanted to take a moment to express my sincere gratitude for the job offer extended to me for the position of [job title]. I am thrilled about the opportunity to join [company name] and to contribute my skills and experience to the team.

I appreciate the time and effort that you and the rest of the hiring team have invested in the hiring process, and I am honored to have been selected for the position. The thoroughness of the process and the way you have kept me informed throughout has made me feel valued and respected.

Thank you again for this opportunity. I look forward to starting my new role and being a part of the [company name] team.

Best regards,

[Your name]