Tax bills are mailed as a convenience to taxpayers in October/November (see RSMo 137.392 above) and are delinquent after December 31st. Payments postmarked by December 31st are considered paid on time. Payments postmarked after December 31st will be returned for interest and penalty for January. Failure to receive a tax bill does not relieve a taxpayer of his/her obligation to pay taxes by December 31st. This is in accordance with the Missouri State Statutes.