Short-Term Investment Ladder Tracker: Never Miss a Maturity or Blow a Concentration Limit

The problem this kills

If you run a short-term investment ladder — a stack of CDs, T-bills, and money-market positions that mature on a rolling schedule — the whole point is timing. Cash comes due, you decide whether to reinvest or use it, and you keep enough rungs spread across enough institutions that you're never caught flat. Done right, it's safe, liquid, and earns real interest. Done in a spreadsheet, it's an accident waiting to happen.

Because that's where most of these ladders live: one workbook, one person, a column of maturity dates that nobody is watching closely. A CD rolls into a no-interest sweep account because the alert was a sticky note that fell off the monitor. Two large positions quietly stack up at the same bank and slide past the FDIC insurance limit without anyone noticing. Month-end comes and someone hand-calculates accrued interest for the GL, gets a day-count convention wrong, and the journal entry is off. And every one of these is invisible until it costs money.

A short-term investment ladder is a treasury function. It deserves a real, governed tool — with maturity alerts that actually fire, concentration limits that are checked automatically, accrued interest computed the same way every month, and a manager who approves the reinvestment plan before cash moves.

What you'll build

A simple internal web app for your treasury team. You load your investments — for each position: the instrument type, the institution, the principal amount, the rate, the purchase date, and the maturity date. The tool sorts them into a maturity ladder (what comes due, and when), computes the yield and the accrued interest to any date you pick, and alerts you ahead of each maturity so cash is never stranded.

It also watches your concentration limits — flagging any institution where your total exposure creeps over your FDIC-style cap — so you catch it before you place the next position, not after. When maturities approach, the tool drafts a reinvestment recommendation, the treasury manager reviews and approves the plan, and only then is it marked as the agreed plan of action. At month-end you export the ladder and a clean interest-income accrual in the columns your GL expects.

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 treasury operation — the instrument types you actually hold, how your institutions and instruments are named and coded, your day-count and accrual conventions, your concentration and insurance limits, how far ahead you want maturity alerts, and the messy exceptions (callable CDs, partial redemptions, rolled positions, brokered vs. direct). It reads a short tailored spec back to you and waits for your thumbs-up before it builds anything — so the ladder matches how your treasury actually works, not a generic template.

From there it walks the agent through the data model, the investment import with duplicate guards, the maturity-ladder builder, the yield and accrued-interest engine, the concentration-limit checks, the maturity alerting, the manager approval gate for reinvestments, and the ladder + accrual exports. Every step ends with a ready-to-copy prompt. There's a full "No API yet?" path that uses a Google Sheet / CSV as the data source and produces clean CSV exports — so you can build and run the whole thing this afternoon, with no connection to a custody or accounting system required.

The governance it includes (this is the point)

This is treasury money, so the controls aren't optional. The plan builds in login so only your team can use the tool, row-level security so you only ever see your own organization's positions, a complete audit trail of who loaded what and who approved which reinvestment, a hard human-approval gate so no reinvestment plan is acted on until the treasury manager signs off, and duplicate guards keyed on the instrument id so the same position can't be loaded — or counted in a concentration total — twice.

Who it's for

Treasury analysts, cash managers, controllers, and finance-owning founders who manage a short-term investment ladder and are tired of trusting it to a spreadsheet and a reminder that may or may not fire. If you can list your current positions and tell me how you calculate interest, you can build this.

You've got this — start with the plan, paste the first prompt, and answer the interview. You'll have your maturity ladder on screen before the afternoon's out.