If you’re going to appeal an assessment, you’re going to have to do some work.
Now, I’ll state up front that I don’t know the local laws and rules where you live, so this might not be useful to you. I’m also going to assume no downward change in the mill rate in your location, so your assessment increase will hit you hard in the pocketbook, and you have a good reason to appeal.
First of all, ask the assessor how he or she arrived at that figure. It may well be that the house has not been assessed for years, or that some owner before you made some improvement that wasn’t inspected until recently, or some such. It is unlikely that the assessor will lower the assessment at this stage; but you should know (heck, you have a right to know) what happened to create the higher assessment.
Then find out about similar homes in your neighbourhood. You said you lived in a townhouse, so that makes things simpler–you can assume that most of the units are pretty much alike. But do a little work and find out anyway.
From a realtor (or perhaps city hall or the assessors themselves), you should be able to get information on all aspects of the units in your neighbourhood–size of lots, plumbing details, electrical details, construction techniques–all that stuff. Use the information to see if other units are physically different from yours. If so, how much? A new flower garden won’t make a difference, but an extra four-piece bathroom or a new front porch will.
What are the assessments of the other units? Are they about the same as your old one (in which case, you’ve got a pretty good argument) or about the same as the new one (in which case, you don’t have much of an argument)? This information should be publicly available at the registry office or the city hall.
If it all checks out–that is, your neighbours have the same unit as you, or perhaps more improved units, but are assessed at around your older value, you’re ready to head for Assessment Review. It will be much like you can imagine–you tell your side of the story, and the assessors tell theirs, and the adjudicator makes a decision.
I’ve found that it can be worth it for John and Jane Public to appeal if they feel it is warranted. The adjudicator will often (though not always) cut the independent homeowner who does the homework and presents his or her own case some slack. Maybe not back to where the original assessment was, but anything is better than 81%.
Good luck!