Custom Invoice and API Integration

I need a customised invoice created and an API integration with the time tracking program Harvest.

Invoice Requirements:
- Format: PDF, Excel, or Word document (please specify your preference)
- Must include:
- Client details
- Project details
- Payment terms

API Integration Tasks:
- Push invoice data to Harvest
- Synchronize project details

Ideal Skills and Experience:
- Experience with API integrations
- Familiarity with Harvest and invoicing software
- Strong attention to detail