People frequently assume that because you (the designer) have used certain fonts in producing some kind of promotion for them, that they are entitled to the fonts that were used. After all, they paid you didn't they? This is one of those things that often gets overlooked or ignored, as no one likes to talk about it. My recommendation though is to put language in your Terms & Conditions, perhaps near the copyright discussion, that explains that fonts have their own licensing requirements. If a question is raised about this, great, take the time to explain it.
Another approach is to be more pro-active at the outset by asking if they (your new client) will want to own the fonts used in their materials. This will lead to a discussion of font licensing and often to a line item addition to you estimate that will include a fee for fonts. Of course, most clients really have no need to own the fonts as they don't have in-house editing capabilities anyway, so they may not be concerned as long as they can have it printed and changed at a later date.
Bottom line – it's good to talk about this one up front.
