I made a handful of ruby scripts to automate exporting subscription transaction data for my SaaS from Stripe, piping it into my accounting tool and reporting to the authorities. There's a script to validate that all paying customers are assigned a "VAT zone" (same country as me, EU or "rest of the world") and help me assign one if they don't (it's a command line tool that provides links to their email domain and Stripe customer data, to help me figure out where they are located). Then there's one to make sure I have a verified VAT number for everyone in a zone where that is a requirement (and warn me if I got a payment where the tax wasn't set up accordingly). One to pull all transactions from a given quarter, by default the last finished one. One to download invoice PDF's for all these transaction and upload them to my accounting tool. One to upload the rest of the transaction data to the accounting tool, categorizing things correctly by vat zone and linking up with the already uploaded PDFs. And finally one to generate a CSV of EU "reverse charge vat" customer transactions to be uploaded to the gov't for reporting purposes.

It started as a single script and has grown into a little suite of related scripts that function a bit like a pipeline, each operating on the same list of transaction data one after the other. All told I've probably spent a week coding and improving them, and they've certainly saved me several months of manual work in the last couple years.