A business bank account is one held in the business's name and used only for its money.
Why a company must have one
A company is a separate legal entity, and its money is its own. Running it through a personal account undermines the separation the entity exists to create — see separating business and personal money.
Why a sole proprietor should have one
There is no legal separation to protect, but every practical benefit remains: substantiating deductions, producing accounts anyone can read, and being able to answer what the business earned without unpicking it from household spending.
Opening one
Generally requires formation documents, the tax identification number, any trade name registration, and identification for the owners — see business name registration.
What to hold alongside it
A business card, so costs are captured without personal cards being involved.
A separate account for money that is owed to someone else — tax withheld, sales tax collected, and any tax reserve. Money that will be someone else's is not available to spend, and holding it separately is the reliable way to stop it being spent.
Choosing between banks
Fees, and particularly the pattern of them: monthly charges, transaction counts, cash deposit limits and charges for deposits above them. A trade taking cash can pay materially more at one bank than another.
Whether the bank connects for automatic transaction import — see bank connection.
Whether they lend to businesses of this size and trade, which matters later — see business credit.
Connecting it
Access is read-only, and credentials are entered with the bank rather than with Omnyra.
Small purchases impractical to put on a card are petty cash, which needs a system precisely because the amounts are small.