If you own and occupy your Nantucket home as your primary residence, you may qualify for the residential tax exemption. For the fiscal year 2012 the dollar amount for the exemption was $1,078.29 Everyone who qualifies receives the exact same credit, regardless of the assessment of the property. To calculate, the average residential value ($1,489,345 for 2012) is multiplied by 20% (the exemption) which equals $297,869. This dollar amount is subtracted from the assessed value of the each qualifying parcel to determine the taxable value. For the fiscal year 2012 there were 2280 parcels that received this exemption.