Seller ID checks

[Temi I.]

At what stage of the transaction do title companies usually request identification from the sellers? Does it vary or should it always be at the offset when the title search is ran?

The reason why I ask is because my title company requests at different stages. With the first transaction it was as soon as they opened the file, but with the second current one they waited until the title commitment came back. Now the sellers are unresponsive and this is holding up the closing.