The list of companies using Instant Interest is a veritable Who’s Who of American business. Twenty-one of the top fifty Fortune 500 companies use Instant Interest. Our customers represent leaders in the following businesses:
| Accounting/tax services | Hotel |
| Advertising, Marketing | Household and Personal Products |
| Aerospace/Defense | Industrial Machinery |
| Airlines | Information Technology and Services |
| Banks | Insurance |
| Beverages | Lawyer |
| Building Materials | Life Science Research |
| Chemicals | Mail, Package and Freight Delivery |
| Construction Materials | Manufacturing: Diversified |
| Diversified Financial | Medical Products |
| Diversified Manufacturing | Metals |
| Diversified Outsourcing Services | Mining, Crude – Oil Production |
| Education | Miscellaneous |
| Electronics, Electrical Equipment | Motor Vehicles and Parts |
| Energy | Oil and Gas Equipment |
| Engineering, Construction | Packaging Containers |
| Entertainment | Petroleum Refining |
| Financial Data Services | Pharmaceuticals |
| Financial Services | Pipelines |
| Financial: Investments | Professional Services |
| Food and Drug Stores | Publishing, Printing |
| Food Consumer Products | Railroads |
| Food Packaging | Real Estate Services |
| Food Production | Retail |
| Food Services | Semiconductors |
| Forest and Paper Products | Telecommunications |
| General Merchandising | Tobacco |
| Health Care Information Technology | Tools |
| Health Care: Insurance and Managed Care | Trucking, Truck Lines |
| Health Care: Medical Facilities | Uniforms |
| Health Care: Pharmacy and Other Services | Utilities: Gas and Electric |
| Home Equipment, Furnishings | Wholesalers |
Whatever your business, if you need to calculate interest on tax overpayments or underpayments, then Instant Interest is for you.