Is the tax assessment of a home equal to market value?

It depends. Re-evaluation of property is not always done yearly. In my town these are done every 5 years. So if the market is improving, your tax assessment could be lower than market value; conversely if the market values are declining, your assessment will be higher. Some towns publish an “equalization ratio” to give a percentage adjustment of their assessment to market. If your equalization ratio is over 100%, the market value is lower than your town assessment.