Client emails me and says "Hey, I want to offer the job to Kathy, but I only have her salary on her past two jobs, can you get her salary from the company before that? That would be helpful to arrive at a fair compensation package for both her and us."
Sounds pretty reasonable, right?
Except it's not the right way to set salary.
If my client wants to retain Kathy, her past salary is irrelevant — the only factor that matters is market rate. And in this search, all the other qualified candidates were within 5% of each other in total compensation--that's market rate. (Here is more information about how to calculate it).