Use Tax Self-Assessment Tracker: Catch the Untaxed Purchases Before the Auditor Does

The problem this kills

Use tax is the compliance gap nobody enjoys owning. A vendor in another state ships you taxable equipment and charges no sales tax. A software subscription renews with zero tax line. A field office buys supplies on a card from a marketplace that didn't collect. Each one is a small thing — and each one quietly creates a use-tax liability your company is supposed to self-assess, accrue, and remit to the state where the item was used.

So once a quarter someone exports a giant AP file, scrolls for the rows where "tax charged" is blank, tries to remember which of those items are even taxable in which state, eyeballs a rate, and types it all into a spreadsheet under deadline. It's slow, it's easy to miss rows, and the misses are exactly what an auditor multiplies by three years and adds penalties to. You don't need to be a developer to stop living this way — you need a tool that does the scan the same way every time and keeps your accountant in charge of what gets booked.

What you'll build

A simple internal web tool. You import two things: your purchases / AP CSV (vendor, item, amount, tax charged, ship-to state) and your taxability + rate reference (which item categories are taxable, what's exempt or for resale, and the use-tax rate by jurisdiction). The tool finds every purchase that looks taxable but had no — or too little — tax charged, computes the use tax owed by jurisdiction, and handles the tricky cases: it separates taxable from exempt and resale categories, and it does partial-tax / rate-differential math when a vendor charged some tax but at a lower rate than your ship-to state requires (you owe the difference). It dedupes on purchase id so the same line can't be assessed twice. Your tax accountant opens a review queue, checks the flagged rows, fixes any miscategorized items, and clicks Approve. Only then does the tool generate a use-tax accrual journal entry and a by-jurisdiction summary you can drop straight into your filing — and feed those amounts into your filing tracker.

What's inside the Implementation Plan

The downloadable plan is a step-by-step file you paste into an AI coding agent. It opens by interviewing you about your business — which system your AP/purchases export comes from, the exact column names in your file, how you record ship-to (and what governs use-tax situs in your business), which categories you treat as taxable vs. exempt vs. resale, your jurisdictions and rate source, your typical and peak purchase volumes, and the messy edge cases — and then it tailors the data model, the taxability logic, and every later step to your answers. This is not a generic template; the agent reflects a short spec back to you and waits for your thumbs-up before it builds anything. From there it walks the agent through the import, the taxable-but-untaxed detection, the by-jurisdiction tax math (including partial-tax rate differentials), the accountant review-and-approve queue, and the accrual + summary export — each step with a ready-to-copy prompt. There's also a fallback so you can build the whole thing today even with no API to your accounting system.

The governance it includes (this is the point)

This is real tax tooling, so it ships with the controls a finance team needs: login so only your team can use it, row-level security so you only ever see your own organization's purchases, a complete audit trail of who reviewed and approved which accruals and when, a hard human-approval gate so no accrual is booked or remitted until your tax accountant signs off, and duplicate guards keyed on purchase id so the same line can't be assessed twice. Items the tool isn't sure about (unknown category, missing ship-to) are flagged for the accountant instead of silently accrued or silently skipped.

Who it's for

Tax and AP staff who own use-tax compliance on untaxed purchases — the people who self-assess and remit, and who'd rather hand an auditor a clean, repeatable workpaper than a stitched-together spreadsheet. If you can describe how your shop decides what's taxable and where, you can build this.

You've got this — start with the plan, paste the first prompt, answer the interview, and you'll see your taxable-but-untaxed queue take shape the same afternoon.