1. For the default case, categorize it like any other business expense. Enter the bill or bank feed transaction, assign it to an Insurance Expense account (Chart of Accounts, New, Expenses as the type, Insurance as the detail type if you don't already have one), and pick a payee. That covers company health plan premiums, employee medical reimbursements, and anything else genuinely paid by the business for the business.
2. Split a mixed insurance bill if it covers more than one thing. A single invoice sometimes bundles health, dental, vision, and even general liability into one payment. Split the transaction line by line so each piece lands in the right expense account instead of all of it dumping into one generic bucket.
3. Stop and check your entity type before categorizing the owner's own health insurance. This is the case that trips people up. A sole proprietor or single-member LLC paying personal health premiums from the business account isn't booking a business expense, it's an owner's draw, even though the payment physically left the business bank account.
4. Handle an S-corp owner's premium as compensation, not a plain expense. If you're taxed as an S-corp and the business pays your health insurance, the IRS treats that as additional wages to you, the owner, not a standalone deductible expense. In practice it's usually run through payroll so it hits your W-2, with your payroll provider handling the mechanics, rather than entered as a straight Insurance Expense transaction.
5. Keep a separate account, or at least a clear sub-account, for owner health insurance. Lumping it in with regular company-paid employee premiums makes it hard for your accountant to tell at a glance what's compensation versus what's a straightforward deductible cost come tax time.