I do some business consulting work through a registered sole proprietorship in the United States. I invoice my clients on a monthly basis through a paypal for business account, and have been transferring the money to an old personal checking account that I had previously only been using as a passthrough for paychecks.

The number of transactions is very low, the account only has money from the consulting business in it, and there are no other income streams going into the account.

I know that it is generally a good idea to have a separate business account, but is there any reason I would need to open up an actual business account for this money?