Notes on real books and AI.
Double-entry bookkeeping, audit-ready business records, and running your books with an AI assistant.
Selling software across the Canada–US border
Digital supplies are where sales-tax rules were stretched furthest to cover something they were not written for. Here is what a Canadian SaaS business actually has to work out.
Cash or accrual — the choice decides what your numbers mean
Cash accounting tells you what moved. Accrual tells you what happened. For most growing businesses the difference between them is the whole picture.
How to design a chart of accounts you will not regret
Most charts of accounts are too detailed in the wrong places and too vague in the ones that matter. The test is whether an account answers a question you actually ask.
Bank reconciliation is a completeness check, not a tick-box exercise
Matching the ledger to the statement proves your books contain everything that happened. Here is what the differences actually mean, and which ones are a problem.
A month-end close that closes
The close is a sequence, not a checklist you can do in any order. Getting the order right is most of what makes a period stay closed once you have signed it off.
The gross-to-net model, and why payroll is three transactions
Payroll looks like one payment. In the books it is an expense, a set of liabilities you are holding for someone else, and later a remittance. Conflating them is why payroll accounts drift.
Sales tax and employer levies by province
A single reference for what each Canadian province charges — GST, HST, PST, QST or RST, plus which five provinces add an employer health tax and which workers' compensation board you deal with.
Input tax credits are an evidence problem, not a maths problem
The arithmetic of claiming back GST/HST is trivial. What gets claims denied on audit is missing documentation and tax claimed on things that were never recoverable.
The $30,000 GST/HST threshold has two tests, and they give different answers
Crossing $30,000 in one quarter ends small-supplier status immediately. Crossing it over four quarters gives you roughly a month. Most explanations skip the difference.
Place of supply — why you charge Ontario's tax from Alberta
The GST/HST rate on a Canadian sale follows your customer, not you. Here are the rules that decide it, and the cases where they surprise people.
Connecting Claude or ChatGPT to your books with MCP
comma is a remote MCP server, so an AI assistant can run your books — scoped to the connecting user's role, fully logged, and revocable in one click.
Why your books should be an immutable ledger
A real ledger never lets a posted entry be silently edited or deleted — corrections happen by reversing. Here's why that matters, and how comma enforces it.