Every ZIP code in the United States, with weather, radar, trivia and the numbers behind it. Five digits since 1963!

ZIP stands for Zone Improvement Plan. The codes went live on July 1, 1963.The lowest ZIP code is 00501 — the IRS in Holtsville, New York.The highest ZIP code is 99950, in Ketchikan, Alaska.Type 07734 into a calculator and turn it upside down: hELLO. It is Keansburg, New Jersey.12345 belongs to one company: General Electric in Schenectady, New York.The first digit is a region: 0 is New England and New Jersey, 9 is the West Coast, Alaska and Hawaii.Mr. ZIP, the cartoon mailman, was the mascot that sold the idea to America.ZIP+4 arrived in 1983 and can narrow a ZIP down to one side of one block.A ZIP code is a mail route, not a place: plenty of them cross county and even state lines.Play ZIP Hunt: guess the secret ZIP code of the day in six tries.
zipcodes.pro — RANKINGS/CO/MOST-TAX-RETURNS

ZIP Codes With the Most Tax Returns Filed in Colorado

What this measures. Number of individual income tax returns filed. A rough proxy for how many households a ZIP code contains, available where census figures are not. Source: IRS Statistics of Income, ZIP code data, data release 2026-10-12.

# ZIP City County Returns filed
1 80134 Parker Douglas 39,750
2 80013 Aurora Arapahoe 37,400
3 80015 Aurora Arapahoe 35,080
4 80634 Greeley Weld 33,510
5 80016 Aurora Arapahoe 33,180
6 80504 Longmont Weld 31,180
7 80022 Commerce City Adams 30,100
8 80219 Denver Denver 29,530
9 80525 Fort Collins Larimer 28,200
10 80020 Broomfield Broomfield 26,970
11 80538 Loveland Larimer 26,760
12 80229 Denver Adams 26,380
13 80011 Aurora Adams 25,550
14 80123 Littleton Jefferson 24,740
15 80233 Denver Adams 24,500
16 80012 Aurora Arapahoe 24,200
17 80918 Colorado Springs El Paso 24,030
18 80127 Littleton Jefferson 23,470
19 80526 Fort Collins Larimer 23,200
20 80550 Windsor Weld 22,990
21 80211 Denver Denver 22,860
22 80602 Brighton Adams 22,720
23 80501 Longmont Boulder 22,480
24 80537 Loveland Larimer 22,320
25 80014 Aurora Arapahoe 22,100
26 80239 Denver Denver 21,600
27 80126 Littleton Douglas 21,490
28 80221 Denver Adams 21,070
29 80601 Brighton Adams 20,870
30 80631 Greeley Weld 20,820
31 80401 Golden Jefferson 20,560
32 80021 Broomfield Jefferson 20,470
33 80524 Fort Collins Larimer 20,110
34 80249 Denver Denver 20,030
35 80031 Westminster Adams 20,000
36 80204 Denver Denver 19,790
37 80205 Denver Denver 19,530
38 80104 Castle Rock Douglas 19,430
39 80227 Denver Jefferson 19,340
40 80220 Denver Denver 19,270
41 80228 Denver Jefferson 19,120
42 80920 Colorado Springs El Paso 19,040
43 80128 Littleton Jefferson 18,950
44 80210 Denver Denver 18,890
45 80112 Englewood Arapahoe 18,830
46 80017 Aurora Arapahoe 18,490
47 80004 Arvada Jefferson 18,410
48 80003 Arvada Jefferson 18,280
49 80906 Colorado Springs El Paso 18,100
50 80916 Colorado Springs El Paso 18,080

Showing the top 50 of 398 ZIP codes in Colorado that have this figure . 80134 ranks 1st at 39,750, against 18,080 in 50th place.

Other rankings for Colorado

Cite this page

zipcodes.pro. “ZIP Codes With the Most Tax Returns Filed in Colorado.” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/rankings/co/most-tax-returns

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