Ask HN: How does your SaaS company handle sales tax?

We are HQ'd in Seattle, WA and subject to WA & Seattle sales taxes for selling SaaS. It's super confusing as to whether we need to collect tax on ALL revenue or just revenue from customers that are also in WA. Also, we need to submit monthly payments via a terrible UI to WA State.

Does anyone have a clean solution for tracking and submitting state sales tax? Could we move our HQ to a different state that doesn't consider SaaS to be subject to sales tax?

Thx!