Benefits and pay are below industry standards.
No 401k match. Stock options take forever to vest, if you are lucky enough to receive them.
Most departments do not receive bonuses or pay raises (I know one employee who has been with the company for 8+ years and has had the same salary for 4+ years), and performance reviews are a joke.
Nepotism is rampant. Upper management will pick favorites and then continually promote those people, despite the fact that they are completely unsuited for the roles. Relatives and friends are also hired and given preferential treatment.
For the majority of employees, you'll be working on Bainbridge Island, which adds an hour each way to your commute. I know quite a few people that want to transfer to the Seattle office, but space is limited and most end up stuck on Bainbridge.
Middle management, while nice people for the most part, are generally unsuited for their roles. This goes back to the nepotism comment above.
Your coworkers are typically just there to get a paycheck and/or experience, and most are looking for better jobs.
Avalara asks hew hires to write them favorable reviews on Glassdoor, which is why most of the reviews here are quite positive. If you are thinking of working at Avalara, I would definitely take time to read through the reviews, it should be pretty easy to recognize which ones were written by people that literally just started working here.
Before HR started asking new hires to do so, the company's ratings were considerably worse (which is why HR started asking in the first place).