Separation of duties

We have a situation where we need to implement a separation of duties for payments received.

Currently, payments are received in the mail and the person opening the mail is also the one recording the transactions that the payments are for. That has to stop.

We are going to have one person (employee A) open the mail and log the payments and another person (employee B) record the transactions to achieve the separation of duties.

My question is this:

Let's say employee A receives and logs a high volume of payments (checks) received in the mail.   After logging them, those payments will have to be passed off to employee B to be processed.  How can it be ensured that employee B receives all of the checks that employee A logged?  Would employee A have to stay in employee B's presence until employee B went through all of the checks and verified (signed off) that (s)he received all of the checks that employee A handled/logged?  What I'm confused about is the procedure for passing off checks from one employee to another and making sure they are both in agreement as to what was given and what was received.
The reason I mentioned a high volume is because it seems very time consuming for employee A to log the checks one by one and then have to sit around and observe employee B going through them one by one during the transfer process.

Thank you.