I think applying best engineering practices to business problems (i.e: unit testing your payroll logic) is a vastly undervalued opportunity and I think offering a payroll API is a fantastic opportunity for companies like CharlieHR to gain this functionality.
1. If we use CharlieHR as an example, how do you tackle building a relationship with them as a service provider (Payroll API) while competing with them on the product side? CharlieHR would need to disclose the relationship to their customers (since the data would be shared) -- do you plan to spin out a separate "brand" for the API?
2. How do you accommodate the inevitable Payroll hell: do you have (or plan to have) a staff of payroll administrators (and accountants?) to handle the edge-cases? Are you insured against any mistakes? Have you encountered any challenges so far / identified any big wins?
Thanks and good-luck, I'll pass this on to our HR team!