Your deductions do not change based on whether you co mingle funds. A deductible expense is deductible regardless of where it is drawn from when it is spent. You do need clear documentation of expenses and reimbursements however. A CPA worth their salt can make sense of deductions regardless of where the money is.as long as you have proper evidence of amounts, dates, and purposes. Maybe it's a thin paper trail that has your CPA nervous, not the co mingling per se.
That being said, a separate account makes things much, much easier. A CPA worth their salt will probably charge you more to dig through your shoebox than they would if presented with organized receipts and a separate account.
Whether it is a business account or a personal account has to do with your business structure. Are you a sole proprietorship? If you've taken no action to create some other entity like a c-corp or an LLC, then you're probably operating as a sole proprietorship. Even if you've set up an LLC, if it's just you as the only member you're probably a sole proprietor for tax purposes.
Your bank will likely have a lot to say about whether you can use a personal account for your sole proprietorship or not. Some will allow it, many will not. You may find that there are transaction limits on a personal account that become problematic at times. Or you may find your bank unwilling to cash a check made out to your sole proprietorship by name without a small business account for that entity. .
If you are operating as an LLC or c-corp you will be unlikely to get your bank to allow that through a personal account.
Edited 1 time(s). Last edit at 12/03/2019 08:54AM by JustForFun.