Form RP-6371-DET: Notice of Assessor’s Determination of Loss of Property Value Explained

Form RP-6371-DET, officially titled Notice of Assessor’s Determination of Loss of Property Value, is a document issued by local assessors in New York State to property owners along Lake Ontario and its connected waterways. Unlike most tax forms that a taxpayer fills out and submits, this one works the other way around: the assessor completes it and sends it to the property owner as a formal response to a prior application for assessment relief.

This form is tied directly to the Lake Ontario flooding relief program created after high water levels caused significant property damage along the shoreline. Property owners who experienced a loss in value due to flooding, erosion, or storm damage could apply for temporary assessment reductions using Form RP-6371-APP. Once that application is filed, the local assessor reviews the claim, inspects the property or the supporting evidence, and then issues RP-6371-DET to communicate their official determination.

Who Receives This Form

Property owners in eligible counties along Lake Ontario and its connected waterways who filed an RP-6371-APP application are the ones who receive Form RP-6371-DET. The form isn’t something you download and fill out on your own initiative — it arrives from the assessor’s office as part of the review process. If you never submitted an assessment relief application for flood-related property damage, you generally won’t need this document at all.

That said, having a fillable version of the form available matters for assessors and local tax offices who need to process multiple determinations efficiently. Since the form is an AcroForm PDF, assessors can type in property details, valuation figures, and determination outcomes directly into the document rather than filling it out by hand, which speeds up processing during periods when many property owners are filing claims at once.

What the Form Contains

Form RP-6371-DET typically includes:

• Identification of the property, including parcel number and owner name
• The assessor’s findings regarding the claimed loss of value
• The dollar amount or percentage of value reduction determined by the assessor
• The effective assessment year for the adjustment
• Space for the assessor’s signature and date of determination

Once a property owner receives this notice, it becomes the official record of how much their assessment will be reduced due to storm or flood-related damage. This determination directly affects the property tax bill for the applicable period, so it’s worth reviewing carefully against your original application to confirm the numbers match your expectations.

When This Form Is Used

The form is used specifically within the timeline set by the Lake Ontario assessment relief program, which was tied to specific flood events. Assessors were required to issue determinations within a set period after receiving applications, so property owners typically saw this notice arrive within weeks or a few months of submitting their RP-6371-APP paperwork. If you’re dealing with older flood damage or a different type of property loss, this particular form may not apply, and you’d want to look into other relief options such as the property tax refund process described in Form RP-556.

What to Do After Receiving It

If you disagree with the assessor’s determination, most jurisdictions allow property owners to challenge the finding through the standard grievance process for assessment disputes. It’s a good idea to keep a copy of both the original RP-6371-APP application and the resulting RP-6371-DET notice together, since you may need to reference both if you file a formal grievance or if questions arise on future tax bills.

Property owners dealing with other storm-related property tax issues in New York, such as damage from Superstorm Sandy, should also check whether they qualify under a separate program described in Form RP-5850, since eligibility and forms differ depending on the specific disaster and waterway involved.