Tools
The toolbelt spec — 22 calculators, one definition, two surfaces.
- Documents
- 1
What each document covers
The tools this spec defines
- Difference diagnoserOut by 8,100? That is divisible by 9 — a transposition. This says which error fits the gap.
- Which invoices make this deposit?A deposit against forty open items. Exact subset-sum over minor units — no floating point.
- Two-list matcherBank against ledger: exact, then reference, then a date window, then one-to-many — and what is left on both sides.
- Duplicate paymentsSame vendor, same amount, close in time — plus the same reference whatever the date.
- Benford & round numbersTwo cheap tests over a pasted column. Neither proves anything; both tell you where to look.
- Depreciation scheduleStraight-line, declining balance or SYD, with the convention that decides the first period.
- Prepaid & deferred releaseA premium paid on the 17th does not release in twelve equal slices. Day-weighted, or even — your call.
- Loan amortisationLevel payment solved, then walked in minor units so the last payment clears the balance exactly.
- Lease — ASC 842 / IFRS 16PV of the payments at your IBR, the liability unwind and the ROU asset — straight-line for a finance lease, the plug to a level cost for an operating one.
- VAT / sales taxGross to net is a division, not a multiplication. The three figures always add back up.
- Margin & markupThey are not the same number, and confusing them is how a price list quietly loses money.
- FX conversion & gain/lossThe rate is the one in your policy, so you type it. No live rate, no network call, no stale surprise.
- Penny-exact allocationSplit 100.00 three ways and get 33.34 / 33.33 / 33.33 — never a cent left in suspense.
- NPV, IRR & XIRRIRR by bisection, so a sign-change-heavy series does not converge on a confident wrong answer.
- Effective vs nominal rate12% compounded monthly is 12.68%. That difference is the covenant you either pass or fail.
- Payment terms & due dates2/10 net 30 is borrowing at 37% a year. This tells you whether to take the discount.
- Day count & proration30/360 is wrong about the calendar and right about the contract. Both are here.
- Journal entry balancerPaste an entry, see the out-of-balance, and copy an import-ready CSV.
- Trial balance checkerBalances — and then the harder question: is anything sitting on the wrong side of its normal?
- Number cleaner(1,234.56) · 1.234,56 · 1,234.56- · $ 1 234.56 · 1.2k → clean signed values, one per line.
- IBAN, routing, VAT, EINChecksums, offline. A valid IBAN is not a real account, and this says so.
- Amount in wordsFor the check, the note, the contract schedule — with the cents as a fraction over 100.
From here
The same material, reached the other way round — by the word, by the component, or by the thing running.