Hi [Client Name],
I want to apologize because I’m running behind on [project or deliverable].
I should have communicated this earlier. The updated delivery date is [new date], and I’m currently focused on completing [specific remaining item].
I understand the delay is inconvenient. If this timing creates a problem on your end, tell me and I’ll do my best to adjust priorities or split delivery into parts.
Thanks for your patience, [Your Name]