No.

If your lawyer told you that, they’re wrong.  Sorry.  Some lawyers think it is safer to list your legal name in your logo and there’s no downside, but they are wrong.

Let’s consult one of the largest law firms in the country, Baker & McKenzie LLP.  Take a look at their homepage.  They don’t even have LLP anywhere on the page!  The legal name of the company is in contracts, tax returns, legal documents, and so on…not the logo.

Look at the homepage of any successful company.  I went to ford.com and there’s no ‘Inc.’ in the logo?!  Is that automaker a sole proprietor?  Does the logo on your car have ‘Inc.’ on it?

Take a look at any piece of clothing with a logo on it.  Take a look at any sports team’s uniform.  Look at ads, billboards, TV commercial…get the idea?

What’s the downside?

By including ‘Inc.’ or ‘L.L.C.’ in your logo, you look like a hack.  You look small and unsophisticated.  You look like you are bragging about filing paperwork with the state you live in.  If you think it’s important to say that you are as big as ‘Brad Miller Design, Inc.’, I’m not impressed.

Why is there a misconception?

You need to disclose who you are legally.  Your company is a legal entity and should be listed correctly.  It shouldn’t be a secret who your company is and what type of legal entity you are.

I’m not a lawyer, and I can’t claim that I have expert legal advice on every issue.  In the same respect, DON’T TAKE DESIGN ADVICE FROM YOUR LAWYER.