Have you consider to use a compatible software solution to automate the sales tax mess?
Quaderno sends automatic receipts every time you get paid and issues credit notes every time you make a refund. Quaderno also notifies you every time you surpass a tax threshold or when a tax rate changes anywhere you sell your products or services. If you sell on channels other than Shopify, it brings all of your tax information into one report. Finally, with Quaderno tax reports, tax filing is a matter of minutes not hours.
Disclaimer: I work at Quaderno. If you have any questions, please feel free t reach out. I'm happy to help.
I also just started a t-shirt e-commerce company using a drop shipper. I'm registered as a single-member LLC (which effects my cases shared below; your business structure might change your requirements). Here's what I learned today:
Finally, obviously, I am not a tax expert, and my above comments should not be taken as legal advice, and I assume no liability for the comments above—as they say, you should consult a tax professional.
Anyway, I hope that's helpful! I spent about 6 hours researching today trying to understand whether I would need to collect and remit taxes to states other than where I operate. It shouldn't be that hard to answer that question.