…on a south branch of White Oak on the south south side as follows. Beginning at a pine thence So67W 140 poles to a branch to three pines thence So7Et 120 poles to a post…to the beginning Containing 100 acres more or less.

A county mapper recently contacted me with a question and not surprisingly I had to learn the answer myself to provide an answer. I am not a mapper nor have I had the opportunity to work closely with mappers, so if you can add to this discussion, please do so below through “Leave a Reply”. While searching for the answer, some documents were revealed that I think will be helpful to others.

The issue involved a county that assesses land based on deeded acres, which may include road right of way. The question was whether there is guidance to help establish a county policy identifying assessment best practice regarding situations where deeded acreage may include road right of way or when deeded acreage varies from calculated acreage.  The answer is, yes.

First, let’s understand the question. When using acreage as a data element in mass appraisal, that data may originate from a deed description, or from actual calculation using mapping techniques and technologies. Which should be used, deeded or calculated? Let’s start with the most general guidance and drill down.

IAAO advises in both Workshop 100 and Course 101 and in their textbook, the following:

If the acreage calculated differs from the deed acreage, the map technician should record the calculated acreage if it falls outside the acceptable range for deed acreage. “Land Identification and Cadastral Maps.” Property Assessment Valuation, Bennett (Eds.) , 3rd ed., International Association of Assessing Officers, 2010, p. 147.

What is meant by “acceptable range”?

The NC Secretary of State, Land Records Division provides a Best Practice manual for some of these issues:


Page 35 of the manual defines deeded, calculated, and assessed acreage. All three are important attributes, with the assessed acreage being the one used for tax purposes.

Page 81 of the manual addresses taxable and non-taxable (including right of way) areas. Non-taxable would refer to the assessed acreage attribute. Note that Appendix C of the  manual includes a reference to an AG opinion supporting the opinion to not include right of way areas in the assessment if the size of parcel is used in assessment. Here is a Property Tax Commission decision also supporting that opinion.

Then, here is the Land Records Division connection with the earlier guidance given by IAAO. Beginning on page 130 of the manual, there is a suggestion that the county adopt a “tolerance”. This is the “acceptable range” mentioned by IAAO. If a county uses deeded acreage to assess property, it’s ok to do so as long as the tolerance, or acceptable range, isn’t exceeded. All of this infers that calculated acreage would be used if the tolerance is exceeded.

What is a good tolerance? My friend Dan Williams in Franklin County shares this language included in their 2018 schedule of values.  John Bridgers with the Land Records Division agrees that these tolerances are not unreasonable.

Deeded vs Calculated Acreage Discrepancies – Franklin County is a “Deeded Acreage” county indicating the County Assessor will list all parcels at the acreage as stated on their respective deeds.  In accordance with the best practices as recommended by the North Carolina Secretary of State, Land Records Division, the County Assessor may resolve discrepancies between Deeded and Calculated acreages using the following tolerance levels:


Parcel Acreage Tolerance Percentage
1 – 5 10%
5 – 20 8%
20 – 50 6%
50+ 4%

Here is additional support for excluding right of way acreage in assessment calculations and for using calculated acreage when it differs from deeded.

1979 AG Opinion– Right of Way should be excluded. (great response, but ended what is cadastral, heh….)

1994 AG letter – Accurate acreage data and size dimensions are preferred for assessment over old deeds that are determined to be less reliable.

Does accurate acreage always matter in value calculations? No. Valuation models used for mass appraisal, most likely in your CAMA software, should use a valuation process that reflects the market in each neighborhood. The models should use “assessed acreage” according to its significance in each market. Some markets of subdivision lots may indicate every lot is the same value even though the sizes differ by 50% or more.  If that’s the market for that neighborhood, it’s correct. There are certainly other neighborhoods with markets indicating square foot (or acres) is the most significant determining factor. Still others with frontage being important (water, view, or street frontage), and likely should rely on front footage as the main value driver with assessed acreage meaning even less.

Consistency and accuracy are paramount. NC counties and appraisers are split regarding whether deeded or calculated acreage is best. But “assessed acreage” should be as written on page 35 of the NCSOS manual, “based on the best information available to the mapper and assessor”. In the end, if the assessor is relying on acreage as a determining factor of value, it should be the correct acreage (within tolerance), and cannot be based on incorrect measurement data from a deed.

Have some mapping fun with this free acreage calculator.

Please leave a Reply below…..