I'm no expert on tax software, but my experience deploying it for accountants is that on-prem tax software is usually updated monthly to incorporate new rules.

I'm no expert on tax software, but my experience deploying it for accountants is that on-prem tax software is usually updated monthly to incorporate new rules. Tax rules are very complicated and often can't just be expressed as an entry in a database. In that context, downloading a fresh set of rules at startup is effectively the same as auto-updating.