In addition to the annual township, county and school tax bills collected by the Tax Collector, there are additional bills called “interim” tax bills that can be issued. Interim tax bills are the result of a list of changes the Tax Collector receives from the Montgomery County Board of Assessment Appeals.
Increases in assessments which result in an interim tax bill can be caused by things such as new construction on a vacant lot, adding on to your home, installing a swimming pool, etc.
Interim tax bills are in addition to the annual tax bills. The due date of the interim tax bill is stated thereon. It is typically NOT the same date as the due date of the annual tax bill.
Of course, if you feel your property should be assessed at a lower amount, you can file an appeal of the assessed value of your home. Appeal forms can be found here:
https://www.montcopa.org/464/Board-of-Assessment-Appeals
If you are successful in appealing your assessed value, you may be eligible for a refund in previously paid taxes or a lower tax bill amount for the current year (if you have not already paid).