There are mistakes a sales manager can make, and then there are the biggest mistakes a sales manager can make. Check out these four costly, and sometimes irreparable, mistakes and then do your best to avoid them.

Mistake #1: The Cell Phone

If you think having a salesperson use their own cell phone to cut costs is a savvy move, think again.

Here’s what really happens: Rather than giving your salesperson a cell phone, you have him use his own. The salesperson then puts his own cell number on his business cards. He proceeds to hand out many of these business advertisements, which is great for your company — as long as he’s working for you.

Long after he leaves the company, people will still be holding on to the business cards. And who do these prospects call once they’re ready to talk — or buy? The sales guy whose number is listed on the card!

What happens if the sales guy has already left your company? You’re out a potential sale. You can’t direct his calls to a new number, so the contact becomes a lost prospect.

Mistake #2: The Email

Let’s say this same sales person has left your company, so you quickly call IT to shut down his email.

Big mistake. You’ve effectively shut off communication entirely with his prospects and leads.

Don’t think that creating an off-the-cuff standard reply saying “the salesperson is no longer with the company” will work either.

Both of these actions lead to abandoned inquiries. The prospect will assume that no one is available to help them with their problem, and they’ll simply move onto another company who has a warm body that will reply to email requests.

Mistake #3: The Autoreply

It seems so innocent, doesn’t it? And so handy at the same time.

Set up the email’s autoreply just like you would for an absence due to vacation or meeting, let prospects know that the sales guy is no longer with the company, and prospect will take action to reach the right person, right? Wrong.

Here’s what you should do instead:

Make sure the salesperson’s email address is redirected to you, the sales manager. Then, you can personally take care of every lead that comes in from that address.

Make it a priority to respond to email inquiries — especially those directed to a salesperson who’s no longer at the company.

Mistake #4: The CRM

Customer relationship management (CRM) systems are a terrific tool. But they’re not foolproof.

In fact, they’re notorious for having incorrect data. So don’t assume the data they spit out is always true. This is especially important when you’re dealing with prospect status. A lot of times, the information is not in real time.

Here’s an example:

You suspect a salesperson is slacking off, even though your CRM shows lots of activity. When you’re in the neighborhood, you stop by a client’s place of business for a face-to-face.

The client is happy to see you, but mostly because he hasn’t seen anyone from your company in months—contrary to the activity the salesperson had been recording in the CRM.

As a sales manager, it’s up to you to spot-check your salespeople, especially if your gut is telling you something is off.

Now that you know some of the biggest mistakes sales managers can make, go out of your way to implement these best sales-manager practices. Provide a company-owned cell phone, optimize email communications, and keep up with CRM data in real time.

What other sales mistakes would you add to the list?