Mountainside Boro NJ property tax rate 2025: 2.100
Mountainside Boro, Union County. 2,858 parcels in the MOD-IV 2026 file. Rate shown is tax year 2025 (latest available — not yet matched to assessment year).
Assessments are tax year 2026; latest published general rate we have is 2025. Estimate uses that rate until the 2026 rate is loaded.
Mountainside Boro at a glance
2,858 parcels are on the 2026 file. The 2025 general rate is 2.100, and the prior rate on file is 2.050 for 2024. A typical class 2 assessment is $636,774. Usable sales with a 2025 deed: 30, median $954,000. The state construction file lists 3,464 permits here. The median class 2 house was built in 1956. A property page adds that parcel’s permits, flood zone, mapped flood elevation, and high and low ground. Owner names are not shown.
How to read a Mountainside Boro bill
Mountainside Boro’s general rate of 2.100 is tax year 2025 on the 2026 assessment file. It is not a 2026 bill. The prior general rate on file is 2.050 for 2024. School, county, and municipal shares of this rate are 48.7%, 23.0%, and 28.3%. The largest slice is schools. In Union County the middle school share for rate year 2025 is 49.0% in Springfield Twp. Class 2 net assessments changed from $1,581,768,505 to $1,593,208,605, up 0.7%, on 2,502 parcels. Usable sales with a 2025 deed: median $954,000 (30 sales). The largest class share of net assessed value is Residential at 63.5%. State school aid is outside these bars.
Building permits in Mountainside Boro
The New Jersey construction-permit file lists 3,464 permits in Mountainside Boro. This file is a full record from 2021 on. Older permits are mostly missing. Work from before then can be missing here and still be at the Mountainside Boro construction office.
2025 general tax rate in Mountainside Boro: 2.100
This general rate is tax year 2025. The assessment file is 2026. It is not a 2026 bill.
In Union County, the median municipality’s school share (rate year 2025) is 49.0%; this town is 48.7%. The largest slice here is schools. State school aid is not in these bars — it reduces the school levy before the rate is struck. All Union towns · How NJ taxes work.
The school percent is the local property-tax levy. The district for this municipality is Mountainside Boro (K-12), FY2027 K–12 aid $1,626,733. Those aid figures are not slices of these bars. Union district table.
Prior year (2024) general rate: 2.050.
Tax on a $200,000 or $500,000 sale in Mountainside Boro
These figures use Mountainside Boro’s own ratio and general rate. How the same sale price is calculated for every town. This is not an appraisal and not a collector bill.
2025
A $500,000 sale at the 2025 ratio of 75.05% would be assessed at about $375,250. At the general rate of 2.100, the estimated tax is $7,880. A $200,000 sale at that same ratio and rate would be assessed at about $150,100, with an estimated tax of $3,152.
In Union County for 2025, the $500,000 bill runs from $7,393 in Summit City to $14,114 in Roselle Boro. The middle bill is $10,396 in Garwood Boro. All Union towns.
See every New Jersey town on the same $200,000 and $500,000 sale for 2025.
Recent usable sales in Mountainside Boro
These are the five newest usable deeds on the 2026 file for Mountainside Boro. A $1 deed and a non-usable SR1A sale are left out. Each parcel stores one sale, so this is not every deed recorded in town.
| Address | Deed date | Sale price | Net assessment |
|---|---|---|---|
| 1085 SYLVAN LANE | 12/2/2025 | $733,000 | $552,400 |
| 242 JUNIPER WAY | 11/10/2025 | $1,116,252 | $782,600 |
| 130 GREENWOOD ROAD | 11/7/2025 | $999,999 | $743,400 |
| 1153 RIDGE DRIVE | 11/3/2025 | $1,000,000 | $723,400 |
| 103 ECHO RIDGE WAY | 10/29/2025 | $938,000 | $704,400 |
Owner names are not shown. The rate year and the assessment file year differ, so this table does not print an estimated tax. This is not a collector’s bill.
Highest estimated tax in Mountainside Boro: $61,559
Residential
The highest residential estimate in Mountainside Boro is $61,559 at 579 HILLSIDE AVENUE, on a net assessment of $2,931,400 and a 2025 general rate of 2.100.
| Address | Class | Net assessment | Rate year | Estimated tax |
|---|---|---|---|---|
| 579 HILLSIDE AVENUE | 2 — Residential (four families or less) | $2,931,400 | 2025 | $61,559 |
| 270 SUMMIT ROAD | 2 — Residential (four families or less) | $2,315,800 | 2025 | $48,632 |
| 1566 ROUTE 22 | 2 — Residential (four families or less) | $1,926,000 | 2025 | $40,446 |
| 443 HILLSIDE AVENUE | 2 — Residential (four families or less) | $1,746,100 | 2025 | $36,668 |
| 153 WILD HEDGE LANE | 2 — Residential (four families or less) | $1,700,900 | 2025 | $35,719 |
Business
The highest business estimate in Mountainside Boro is $524,315 at 1046 SPRINGFIELD AVE, on a net assessment of $24,967,400 and a 2025 general rate of 2.100.
| Address | Class | Net assessment | Rate year | Estimated tax |
|---|---|---|---|---|
| 1046 SPRINGFIELD AVE | 4A — Commercial | $24,967,400 | 2025 | $524,315 |
| 1350 ROUTE 22 | 4A — Commercial | $21,558,200 | 2025 | $452,722 |
| 1180 ROUTE 22 | 4A — Commercial | $11,250,000 | 2025 | $236,250 |
| 200 SHEFFIELD STREET | 4A — Commercial | $10,992,000 | 2025 | $230,832 |
| 253 SHEFFIELD STREET | 4B — Industrial | $10,290,000 | 2025 | $216,090 |
Owner names are not shown. Every parcel in this town uses the same rate, so the highest tax is the highest assessment. Commercial and industrial parcels (class 4A and 4B) are the business list. Apartment buildings are class 4C and are not in that list. This is not a collector’s bill.
Ratable base in Mountainside Boro, typical class 2 assessment $636,774
Class 2 residential in the MOD-IV file: 2,502 parcels, average net assessment $636,774.
How assessments changed
Class 2 residential net assessments changed from $1,581,768,505 to $1,593,208,605, up 0.7%, on 2,502 parcels that have both a prior net and a 2026 net. This is the assessment roll, not an appraisal.
Among 30 usable recorded sales whose latest deed on this file is in 2025, the median price is $954,000. A $1 deed and a non-usable SR1A sale are left out. Each parcel stores one sale, so this is not every deed recorded that year.
Share of net assessed value by property class (MOD-IV). Not a school-quality rating.
| Class | Parcels | Net assessed | % of net |
|---|---|---|---|
| Residential 2 | 2,502 | $1,593,208,605 | 63.5% |
| Vacant land 1 | 189 | $586,170,800 | 23.3% |
| Commercial 4A | 114 | $217,280,600 | 8.7% |
| Industrial 4B | 52 | $113,067,600 | 4.5% |
| Other / unclassified other | 1 | $1,091,147 | 0.0% |
Housing stock in Mountainside Boro, median year built 1956
On the 2026 file, class 2 houses in Mountainside Boro with a year built have a median year of 1956, about 70 years old. Of those 2,490 houses, the largest share was built 1940–1959. This is the assessor’s year built. It is not a ranking of towns.
By parcel count, Residential 87.5%, Vacant land 6.6%, Commercial 4.0%, Industrial 1.8%, Other / unclassified <0.1%. Those percentages are a count of parcels, not a share of tax dollars. The class table uses the tax-base share.
Year built
Assessor building line
Grouped from the assessor’s building abbreviation. One-family, two-family, and condo are the codes that read clearly. Other codes stay in their own group. This is not a bedroom count, and square feet are left off because most records do not include them.