I have a tax worksheet that is being used to show the assessed tax on
housing units for '12-'15, including any amount paid for each of those
years. Right now I have 8 columns of numeric data: assessed tax and paid
tax for each of the 4 years. I have two questions about how to improve
on this due to a complication. Some addresses have two rows, one for an
owner who sold and one for the purchasing owner, when a unit was sold
and purchased in a tax fiscal year. Some owners will have 0s as the
assessed tax due for any years following the sales year as they were no
lonnger the owner.

The worksheet currently has conditional formatting setting alternating
rows to white or a light gray background color, and all of the columns
are set to numeric.

The person who is working with the worksheet asked if it would be
possible to use white text on a dark grey or black background to format
the "0" entries for the years when an original owner no longer owned the
property, e.g if Bob A. owned unit 3 in 2012, then sold it in 2013, he
would ow $0 of the assessed taxes for 2014 and 2015.

What is the preferred accounting approach to something like this, so the
person working with the worksheet can quickly see that taxes in
subsequent years after a sale are not billed to the seller? Is the
approach requested by the worker a good one (dark cell background
colors) or is there a better way? I have zero bookkeeping or accounting
training or experience. Should I put an "n/a" or "n/r" (not resident) in
the cells, use a white zero on a dark background, use "---", or
something else? If it was non-numeric I would have to change the cells
to general or text, then check for numeric entry or "n/?" when doing the
calculations.

Thanks for your thoughts!
Mike