An LLC should keep a separate business bank account. It isn't always a strict federal legal requirement, but commingling personal and business funds can pierce the LLC's liability shield, complicates taxes, and makes you ineligible for most business funding — lenders verify revenue through business bank statements. In practice, a dedicated account is essential.
There is no single federal law that says an LLC must have a separate bank account. But the entire point of an LLC is the liability shield between you and the business — and courts can disregard that shield ("piercing the corporate veil") when an owner commingles personal and business funds. A dedicated account is how you keep the separation that protects your personal assets.
Most small-business and revenue-based lenders underwrite on business bank statements — they need to see the LLC's deposits, average daily balance, and cash-flow consistency. If your business revenue runs through a personal account mixed with personal spending, underwriters can't isolate the business's financial picture, and the file usually can't be approved.
A separate account makes deductible business expenses clean to track and substantiate, which the IRS expects if your deductions are ever examined. It also simplifies bookkeeping, owner draws, and estimated taxes.