As the economy has slowed, more homeowners are completing additions and other projects without permits. They do the work themselves or use a contractor who goes along. Or maybe they don’t seek final approval.

Often, owners do it because they don’t want to pay increased taxes on the extra square footage or other improvements, say Bill Gallagher of the Superior School of Real Estate and Gene Morton, director of inspections for Mecklenburg County.

The issue has worsened in the past four or five years, Gallagher said, and is so important that one portion of his licensing update course for real estate agents is devoted to permitting.

And agents absolutely should disclose any discrepancy when their measurement of square footage doesn’t match tax records. “If it’s measuring 3,000 (square feet), and the tax records say it’s only 2,200, where are we getting this extra 800 square feet from? Red flag!”

Buyers and sellers face legal implications, too.

If you’re buying, be sure to check the permit history for any property you’re considering. It’s easily available online. Don’t wait for the flag.

Here are 5 key things you need to know about building permits, explained by Morton:

1. If an addition is listed on the property’s online tax record, that likely means the permitting was proper. You might see quirks. The work might only be half complete at the time of a tax assessment, for instance, but that should be noted.

2. Generally, permitting history goes back six or seven years.

3. The current owner is responsible for bringing a property up to code, even if a previous owner did the work without a permit. “Yes, and people don’t like to hear that,” Morton said. The current owner can seek relief in court, of course, taking action against those responsible for the improper work.

4. The homeowner should not take out the permit if he’s not doing the work. There are some gray areas in this portion of the law, Morton said. The owner is still ultimately responsible but, as the work is under way, the permit holder – the contractor – is responsible for seeing that it’s done properly. “If I were an owner, I would certainly want the contractor to obtain the permit,” he said.

5. If you’re having work done by a contractor, don’t write the final check until you’re sure the work has received final approval from inspectors.