A penalty of 10% shall be added to the face
amount of all real estate taxes not paid within four months after
the date of the tax notice. The date of tax notice, as stipulated
in Section 10 of the Local Tax Collection Law, has been interpreted to mean the date the notice is mailed
to the taxpayer, not the date printed on the notice.
The penalty added to the tax after four months
becomes part of the tax due and is included in the base on which all
other delinquent interest and penalties are calculated.