A few years back, a CPA (whose system was hacked) said at an IRS forum he had $100,000 worth of coverage and ended up with over $300,000 in costs. If you do partnerships and corps, there is a multiplier effect from every SSN in your system. So I'd say ballpark $500k in coverage, more or less depending on your practice. And ask if coverage includes them coming in and de-bugging your system.