Supplemental Property Tax on a Flip Property

[Matthew Mirkin]

This is my first flip property so I've never had to deal with this before.  I purchased the house in June 2016, for ~$250k, refurbished it and resold it December 2016, for ~$350k.  Property taxes were paid through escrow for both purchase and resale however, the property tax had only ever been calculated from Original assessed Value (the value before my purchase) ~$150k.  After I resold the home I received a Supplemental Property Tax bill using the price I paid for the house in June (~$250k) as the new assessed value.  They want me to pay ~$1000 for the increased assessed value, half at the end of Jan 2017 and the other half in May 2017.

Is this Supplemental Prop Tax my responsibility? Both payments? Is it something that should be prorated for the time I owned the house 6/2016 through 12/2016, not the entire year?

I'd love some advice from people that have had to deal with issue.  The property is in Lancaster, CA, not sure if that matters.

Thanks in advance,

Matt