| East End Disability Associates, Inc. | Health Care and Social Assistance | $3,127,842 | $3,169,404 | 500 | N/A |  Research |
| Riverhead Care Center, LLC | Health Care and Social Assistance | $2,442,353 | $2,287,299 | 233 | $73.1M | Research |
| Aid to the Developmentally Disabled INC | Health Care and Social Assistance | $1,755,700 | $1,769,938 | 295 | N/A | Research |
| Cornell Cooperative Extension Association of Suffolk County | Educational Services | $1,500,000 | $1,513,292 | 191 | N/A | Research |
| Cornell Cooperative Extension of Suffolk | Educational Services | $1,500,000 | $1,512,863 | 191 | N/A | Research |
| Riverhead Motors Inc. | Retail Trade | $1,406,500 | $1,417,752 | 82 | $20.7M | Research |
| Aid to the Developmentally Disabled INC | Health Care and Social Assistance | $1,400,000 | $1,410,510 | 264 | N/A | Research |
| Garsten Motors INC | Retail Trade | $1,326,647 | $1,344,262 | 103 | $26.0M | Research |
| Atlantis Marine World L.l.c. | Arts, Entertainment, and Recreation | $1,270,702 | $1,283,974 | 103 | $15.7M | Research |
| Atlantis Marine World, L.l.c. | Arts, Entertainment, and Recreation | $1,270,702 | $1,287,221 | 103 | $15.7M | Research |
| Twomey Latham Shea Kelley Dubin & Quartararo, LLP | Professional, Scientific, and Technical Services | $1,158,400 | $1,168,207 | 51 | $12.4M | Research |
| Tll Motors, Inc. | Retail Trade | $1,114,293 | $1,122,526 | 67 | $16.9M | Research |
| Tll Motors INC | Retail Trade | $1,114,292 | $1,121,161 | 67 | $16.9M | Research |
| Timothy Hill Childrens | Health Care and Social Assistance | $1,065,573 | $1,082,651 | 124 | N/A | Research |
| Timothy Hill Children's Ranch, Inc. | Health Care and Social Assistance | $1,025,000 | $1,035,563 | 124 | N/A | Research |
| Eagle Auto-Mall Sales, Inc. | Retail Trade | $973,600 | $982,741 | 85 | $21.4M | Research |
| Riverhead Auto Mall Ltd. | Retail Trade | $937,500 | $945,651 | 73 | $18.4M | Research |
| Riverhead Auto Mall Ltd | Retail Trade | $880,410 | $887,043 | 72 | $18.1M | Research |
| Jaral East End Hotel Corp | Accommodation and Food Services | $739,081 | $744,528 | 62 | $19.4M | Research |
| Riverhead Motors LLC | Retail Trade | $730,673 | $738,848 | 55 | $13.9M | Research |
| Terry Contrcting Corp. | Construction | $573,700 | $578,672 | 24 | $9.0M | Research |
| New Leaf Landscape Maintenance, LLC | Construction | $562,700 | $568,003 | 44 | $15.0M | Research |
| Terry Contracting & Materials, Inc. | Construction | $554,200 | $558,788 | 31 | $11.6M | Research |
| 3631 Food Services Corp | Accommodation and Food Services | $540,498 | $546,263 | 120 | $21.3M | Research |
| Jaral East End Hotel Corp | Accommodation and Food Services | $528,000 | $531,804 | 83 | $26.0M | Research |