Writing the appeal so it is decided in your favour on paper
Many appeals never get a hearing. Write as though yours will not.
A large share of Illinois appeals are decided on the documents. Assume nobody will hear you speak.
Lead with the request
First sentence: what you own, what it is assessed at, what you want it assessed at. A reader who stops after one sentence should know what you are asking for.
Name the ground
Uniformity, market value, or factual error. One of them. An appeal arguing all three reads as an owner hoping something sticks, and dilutes whichever was strongest.
Show the arithmetic
Do not make the reader compute anything. If your requested value comes from the median assessed rate of four comparables applied to your square footage, write that line out with the numbers in it.
Keep it to one page of prose
Tables and records can run long. The argument should not.
Be unemotional
No history of your tax bills, no comment on the assessor, no mention of what you can afford. It is not that the board is unsympathetic — it is that none of it is within their authority, and including it signals you may not know what is.
Close with the specific request
Repeat the number. Make granting it the easiest thing the reader can do.