How to report square footage on a BPO when the records disagree

KW Default Solutions

Last updated October 30, 2026

A BPO is an agent's written estimate of a home's probable sale price, done for a client like a lender. Size feeds straight into that price. Someone on the client's side usually checks the report. That reviewer will likely ask about any gap between your number and the records.

What you'll be able to do: pick the right number, explain the gap and write a note that shows your sources.

The decision rule

Work through these steps in order.

Two things stay the same at every step. Don't make up a measurement you didn't take. Don't average the numbers to split the difference, since an average isn't a source.

1. What does the client's form actually ask for?

Ask: Which size fields are on this form, and do the instructions name a source?

Check: The order, the form and any instructions that came with it.

The company that ordered the BPO is your client. Its form and instructions come first. A REALTOR® is a member of the National Association of REALTORS® (NAR). For REALTORS®, the NAR Code of Ethics lists what a price opinion should include. It also says the client can require a specific type of report or different data.

Read every size field first. A form may ask for above-grade area and basement area on separate lines. Above grade means floors fully above the ground outside. Some forms ask for a total.

If the form doesn't say which source to use, ask before you guess.

Script (to the client): "Your form asks for living area, but the tax record and the old listing disagree. Which source would you like me to use"

2. Where does each number come from?

Ask: What are my sources, and how was each number made?

Check: The county tax or assessor record, the prior MLS listing and any measurement you took.

Most size numbers come from one of three places:

• The tax record: the county assessor's file on the home. The assessor is the local office that values homes for property tax.
• The old listing: what the last listing agent entered in the multiple listing service (MLS).
• Your own measurement: what you measured on site, if the order allowed it.

You often won't know how a number was made. Fannie Mae is a company that buys home loans from lenders and sets rules for them. It notes that MLS and assessor sizes may not follow a set standard. It also says an appraiser may not know what method an agent or assessor used.

So treat each number as a report from a source. Write down who said it and when.

Script (in the report): "Tax record shows 1,850 sq ft. The 2019 MLS listing shows 2,240 sq ft."

3. Why don't the numbers match?

Ask: What part of the house is one source counting that another one isn't?

Check: Your photos, the old listing's room list and what you saw on site.

Sources often disagree because they count different spaces. A basement, a finished attic or a converted garage may be in one number and not another.

One measuring standard shows how much these choices matter. The American National Standards Institute (ANSI) publishes a home measuring standard called ANSI Z765-2021. Fannie Mae requires appraisers to use it for many appraisals. Under that standard, as Fannie Mae describes it:

• Any level that is partly below ground is reported as below-grade area.
• An opening to the floor below, like a two-story foyer, isn't counted.
• Finished areas need a ceiling at least 7 feet high, with some rules for sloped ceilings.
• Stairs count with the floor they go down from.

Use this list to spot why numbers differ. It's an appraisal rule. It doesn't tell you how to fill in a BPO.

Script (in the report): "The 2019 listing appears to include the finished basement."

4. Should you measure, and what can you say about it?

Ask: Does this order let me measure, and can I reach what I need to measure?

Check: The inspection type and access instructions on the order.

On an exterior BPO, you view the home from outside only. If the order and access allow it, you may be able to measure the outside walls of the main level. You can't measure a basement or check which rooms are finished.

On an interior BPO, you go inside with approved access. You still aren't an appraiser. If you measure, write down how you did it and what you included.

Fannie Mae's ANSI rule is written for appraisers. Don't say you followed ANSI unless the client asked for it and you know how to apply it.

If you didn't measure a space, say so. That line protects the client and you.

Script (in the report, exterior BPO): "Main level measured from outside at about 38 ft by 49 ft. Basement not measured."

5. Which number goes on the form?

Ask: Which single number can I support best, given the client's instructions?

Check: The decision rule above and the client's answer from section 1.

If the client named a source, use it, even if your own measurement is a bit different. Then note your number in the comments.

If the client left it to you, pick the number you can support and say why. A recent measurement you took and can describe may be stronger than a number with no known method. Explain your choice in one or two plain sentences.

Keep spaces where the form puts them. If the form has a basement line, put basement area there.

Script (to the client, when you see a big gap): "The listing is about 390 sq ft larger than the tax record. Should I comment on it"

6. How do you write the report note?

Ask: Could a reviewer read my note and see exactly where each number came from?

Check: The comments box on the client's form.

A good note covers four things. Which number you used and its source. The other numbers and their sources. Why they may differ. What you didn't verify.

NAR's Code of Ethics asks REALTORS® to avoid exaggeration, misrepresentation or concealment of pertinent facts about a property. A clear note keeps the discrepancy out in the open.

Here's a sample note you can adapt:

Script (to the client, if asked to drop the note): "I'm happy to shorten it. I'd like to keep the sources, since the numbers don't match."

Worked example: one ranch home, three sizes

This example is fictional. The home is a one-story ranch with a basement. The order is an exterior BPO.

Here's the math:

• Listing minus tax record: 2,240 minus 1,850 equals 390 sq ft.
• Agent's measurement: 38 times 49 equals 1,862 sq ft.
• Agent's measurement minus tax record: 1,862 minus 1,850 equals 12 sq ft. That's under 1% of 1,850.

The form has separate lines for above-grade area and basement. The instructions don't name a source, so the agent asks. The client says to use the tax record and comment on any gap.

The agent enters 1,850 sq ft as above-grade area. On the basement line, the agent enters 390 sq ft, labeled as from the 2019 listing and not measured. The note looks like the sample above.

What the square footage line doesn't do

• It doesn't make your BPO an appraisal. NAR says a BPO must make clear to the client that it isn't one.
• It doesn't correct the tax record. Your note explains the gap. It doesn't change the county's file.
• It doesn't tell anyone whether an addition had permits. If you see one that looks newer, describe it and ask the client how to report it.

Naming traps

• "Square footage," "living area" and "GLA" may not mean the same thing. GLA is short for gross living area. Fannie Mae now uses "above-grade finished area" and "below-grade finished area" in its appraisal rules. Read each label on the form.
• "Total" in an old listing may include a basement. Check the listing's room list and remarks before you compare.
• ANSI Z765 isn't a law. It's a measuring standard that Fannie Mae requires appraisers to use for many appraisals.
• A condo in an apartment building is measured differently. For appraisals, Fannie Mae uses inside wall measurements for those units, not ANSI.

Practice: what would you do?

Here are five fictional situations. Decide, then check the answer.

1. The order is exterior only. The tax record says 1,400 sq ft and the listing says 1,700. The form doesn't name a source. What you'd do: Ask the client which source to use. Report that number and note the other one. Say interior space wasn't verified.
2. The homeowner tells you the house is 2,500 sq ft. What you'd do: Treat it as what a source said, not a fact. List it in your note as owner-reported, along with your other sources.
3. The form says to use public records. Your own measurement came out 120 sq ft larger. What you'd do: Enter the public record number. Note your measurement and how you took it.
4. The old listing counted a finished attic with low, sloped ceilings. What you'd do: Describe the attic in your note. Say the listing seems to include it. Follow the form on where it goes.
5. You're tempted to average three different sizes. What you'd do: Don't. Pick one source using the decision rule and list the others.

Next step

If you're working a BPO like this and get stuck on which number to use, we're happy to help you think it through.

Reach out to the KWDS team

Who we are

KW Default Solutions (KWDS) helps Keller Williams agents find and handle listings tied to default. That includes homeowners behind on the mortgage, short sales, bank-owned homes and homes owned by companies or investors. We also train agents to do this work. Most of our opportunities are for Keller Williams agents.

General U.S. real estate education, not legal or appraisal advice. State law, your broker and each client's form decide how you report size on a BPO. All examples are fictional. Ask your broker or a local appraiser about a specific home.

Sources:

• Fannie Mae Selling Guide: B4-1.3-05, Improvements Section of the Appraisal Report
• Fannie Mae: Standardizing Property Measuring Guidelines, updated guidance and FAQs (Sept. 4, 2025)
• Fannie Mae Selling Guide: Glossary, broker price opinion (BPO)
• NAR: 2026 Code of Ethics and Standards of Practice (Article 2, Standard of Practice 11-1)
• NAR: Responsible valuation policy