THE DEADLINE to apply for a homestead exemption on your property taxes is Sept. 13, yet thousands of Philadelphia homeowners have not applied and may miss out on big savings.

If you're unfamiliar with the tax break, here are some answers:

Q: What is a homestead exemption?

A: The homestead exemption shaves $30,000 off the assessed value of your property and your tax bill is calculated from the lower amount. With the exemption, a house assessed at $100,000 in Philadelphia, for example, would be taxed on only $70,000, reducing the tax bill from $1,340 to $938.

Q: Who can get a homestead exemption?

A: Any person who owns and lives in a property as their primary residence. Vacant lots, rental properties and properties owned by corporations do not qualify for the exemption.

You're also restricted to one exemption.

The Daily News earlier this year reported that hundreds of such properties have mistakenly received the exemption in past years, but the Office of Property Assessment's deputy administrator of programs and policies, Kathryn Dreher, said that her agency is working to weed out ineligible properties.

Q: Can I get the exemption if I'm behind on my property tax?

A: Yes. Unpaid taxes are no barrier to qualification and there are more than 5,000 homeowners with five or more years of delinquency who have received it.

Q: Can I have both the homestead exemption and be in the Longtime Owner Occupants Program (LOOP, which offers a tax reduction based on income and length of residency)?

A: Although the city's website says yes, the real answer, according to Dreher, is "no."

Roughly 12,000 homeowners were dropped from the homestead program in 2014 when they were approved for the LOOP.

Q: I already have LOOP. Should I switch to the homestead?

A: That depends. Most homeowners see better savings with LOOP, but data the Daily News have collected indicates that more than 1,000 residents would see greater savings by switching to the homestead.

Under LOOP, your tax is calculated by multiplying your 2013 market value by three. To get your taxable amount under homestead, subtract $30,000 from your 2015 market value. Multiply each figure by 1.34 percent (.0134) to get the tax.

For example, say your house was valued at $33,500 for 2013 (before the citywide reassessment) and $100,000 for 2015 (after assessments were updated). Without either exemption, your tax bill would be $1,340. Under LOOP, your tax bill would be $1,327. But with a homestead, your bill would be only $938, a savings of $402.

Q: My house has a 10-year tax abatement. Can I get a homestead exemption?

A: No. Beginning in 2015, thanks to recently enacted state legislation, properties with abatements will become ineligible for the homestead. Affected homeowners can reapply once their abatement runs out.

Q: How do I apply for a homestead exemption?

A: Anyone interested in signing up should call the Homestead Hotline at 215-686-9200.