Mixing business and personal finances is one of the most common habits I see in new business owners, and it's rarely intentional — it's just easier in the beginning. One card, one account, sort it out later. I understand the instinct. I don't recommend it.
Here's the actual cost. It muddies your real profitability, because you can't tell what the business is spending versus what you are. It makes tax time slower and more expensive, because someone — you or your accountant — has to untangle every transaction after the fact. And if you're an LLC, it can chip away at the legal separation that structure is supposed to give you.
The fix takes an afternoon: open a dedicated business account, get a business card, and run every dollar of the business through it from that point forward. It won't undo the tangle in your history, but it stops the problem from growing, and it's the single easiest habit that makes your books — and your decisions — trustworthy going forward.
