Grain is a free iPhone application that provides a line of credit to your existing checking account. The app is developed by Grain Technology Inc. and is available under the Business and Productivity category in the App Store. With Grain, you can get pre-approved for credit in minutes, without having your credit score checked or being issued a physical card.

Grain offers several features, including the ability to transfer credit to your linked checking account instantly and use it as cash, personalized credit tips to help you improve your credit score, and smarter auto-pay that makes monthly minimum payments for you at the best time during your billing cycle. Grain also reports your account activity to all three credit bureaus every month, thus helping you build your credit score over time. The app also takes security seriously and protects your data with 256-bit bank-level encryption.

While Grain charges a 15% APR and 1% finance charge on credit advances, it may charge some applicants a one-time sign-up fee and a monthly service fee. The app's credit offer is dependent on cash flow in your linked checking account, and it may require a security deposit. Grain's customer support is available through the app and its website. Overall, Grain is a useful app for those looking to build their credit score and manage their finances more efficiently.