Dear [Name]:
It's relatively easy to determine how much property insurance a firm should carry. It's more difficult to determine how much to insure against employee dishonesty, although various formulas have been devised by insurance people, accountants and bankers.
Rather than increasing your blanket bond on all employees at what might be a sizable additional premium, I have another alternative to propose. For a comparatively small cost, we can increase the limits on just certain positions in your firm.
I'll call you in the next few days to see when it would be convenient for you to discuss this option.
Sincerely,