Font licensing is the most ignored legal risk in design, and the letters do arrive. Foundries monitor usage, and the invoices are not small. Almost all of it comes from a handful of misunderstandings.
You license fonts, you do not buy them
Paying for a font buys permission to use it in specific ways. The permissions are in the licence, and they vary enormously between foundries. Read it once per font. It takes two minutes.
The licence types that matter
Desktop. Install it and make artwork. Usually limited by number of workstations.
Webfont. Separate licence for serving it on a website, often priced by monthly pageviews.
App and embedding. Putting the font inside software, a game, or an ebook is a separate permission again.
Broadcast and large-scale commercial. Video, packaging runs and out-of-home advertising can require an extended licence.
The mistakes I see most
"Free for personal use" used commercially. The most common one by far. A client logo is commercial, always. Free download sites are full of these and the wording is easy to skim past.
Sending the font file to the client. Your desktop licence usually covers you, not them. If they need the font, they buy their own licence. Point them to the foundry.
Sharing across a team on one licence. Seat counts are real. Five designers usually means five seats.
Assuming a desktop licence covers the website. It generally does not.
Trusting bundled fonts. Fonts that arrived with a template, a plugin or a marketplace theme may not be licensed for what you are doing.
How to stay safe
Convert logo lettering to outlines — a logo drawn from letterforms is generally fine once outlined, but check the foundry terms, because a few restrict logo use explicitly.
Keep receipts and licence PDFs in the project folder. If anyone ever asks, you can answer in one email.
Tell the client in writing which fonts the brand uses and that they need their own licence for internal use. Put it in the guideline sheet.
When in doubt, use open licensed fonts. Google Fonts and other open families are free for commercial work, including logos, and some of them are excellent.
Two minutes of reading protects the whole project. It is the cheapest insurance in design.