I often have sales people ask me if it's o.k. to tell someone, "I don't know the answer to that question". I always tell them "sure it is, in fact it's a lot better than trying to make something up that could backfire or be wrong!" No one knows everything (well, almost no one!) and no one expects you to have an answer to every question. In fact not having all the answers will make you seem a little more "human" and probably set people at ease...besides nobody likes a "know it all".
However, not having the answer and saying "I don't know" can become a problem when you've said it ten times and your prospect/customer begins to feel that you bring them no value. In a business that has highly complex products or services that require a lot of technical knowledge this can become a real problem for both sales people as well as their sales managers.
For sales people, lack of product knowledge can create "call reluctance" because not knowing the answer over and over again can make people feel like they are "failing". It also extends what we refer to as "ramp up time". Ramp up time refers to the length of time required to learn all of the product knowledge required to be able to answer questions and be effective on sales calls. In some cases, this could make the time it takes a sales person to "get ready" to make calls extremely long. In fact in some situations almost impossible when you consider some of the companies that have literally thousands of products, how could anyone know everything?
So when you get a questions that you don't have an answer to instead of saying "I don't know..." try finding out why they asked. Instead of answering or not knowing, simply say "that sounds important, why did you ask"? You might be surprised by what you find out.
Here is a hypothetical example that relates to a company that sells drill bits:
How long should I expect one of your carbide drill bits to last?
Now, let's suppose you don't know. You could say "I don't' know, let me get back to you". You end up providing little value, lengthen the selling cycle and leave your prospect "vulnerable" to someone else who might have the answer.
Or, you could say, "that sounds important, why did you ask". You might hear something like this:
Our current supplier can't seem to get us anything that will last and we are forced to slow down production because we have to stop and change drill bits to often".
Now you've found the real reason they asked the question and can have a better discussion on what might solve the problem. So next time don't be so quick to say "I don't' know", instead of giving an answer try asking a question!
Action Step: Create a list of questions that you think you might get and practice this technique.