Last reviewed: 2026-05-19

BGN mode on the BA II Plus

The small BGN indicator in the top-right corner of the BA II Plus screen is the most common cause of a CFA candidate getting a Time Value of Money (TVM) annuity answer one period of interest too high. Once a candidate switches BGN on, the setting persists through power-off. Every TVM compute that follows treats payments as occurring at the start of each period rather than the end.

This page explains when BGN is the right mode, how to spot it during a problem, and how to switch back to END with two keystrokes. Charterly's free BA II Plus calculator catches this state under rule M1 in its mistake-detection layer.

When BGN is the right answer

BGN sets the calculator to annuity due mode, which is the convention that each payment occurs at the start of its period rather than the end. Three exam contexts use annuity due:

  1. Lease payments. Most operating lease problems pay rent at the start of each month.
  2. Beginning-of-period pension or retirement contributions. Some problems specify that the candidate deposits at the start of each year before the first interest accrual.
  3. An explicit annuity-due variant of an otherwise ordinary problem. The question stem will say "annuity due" or "payments at the beginning of each period."

Most CFA TVM problems are ordinary annuities, which means payments at the end of each period. END is the correct mode for those.

A worked comparison

Problem. Five payments of 1,000 at 6 percent per year. Compute Future Value (FV).

END mode (ordinary annuity):

  1. 2nd then BGN. Press 2nd then SET until the screen reads END. Press 2nd then QUIT.
  2. 5 then N. 6 then I/Y. 0 then PV. 1000 then +/- then PMT.
  3. CPT then FV.

Expected FV: 5,637.0930.

BGN mode (annuity due):

  1. 2nd then BGN. Press 2nd then SET until the screen reads BGN. Press 2nd then QUIT.
  2. (TVM registers unchanged from the END run.)
  3. CPT then FV.

Expected FV: 5,975.3185.

The difference is 5,975.3185 - 5,637.0930 = 338.2256, which is exactly one extra period of interest applied to the END answer (5,637.0930 × 0.06 = 338.2256). That is the mechanical signature of BGN running on a problem that expected END.

How to switch back to END

Two keystroke paths:

  • Path A (toggle through the dialog). 2nd then BGN. Press 2nd then SET. The screen toggles between END and BGN. Press 2nd then QUIT.
  • Path B (full reset). 2nd then RESET. ENTER. This restores every BA II Plus default including the decimal places and Periods per Year, which is destructive if you set those on purpose. Use Path A unless you also want a full reset.

The BGN annunciator on the screen disappears the moment END is active.

How Charterly catches this

The Charterly engine looks at paymentMode on every TVM compute. If the mode is BGN, the calculator surfaces a non-blocking warning (rule M1): "Annuity due mode is active. If your problem expects end of period payments, switch back to END." The result is always shown. The warning is dismissable for the current session, and the global setting can be turned off from Settings.

For HP 12C candidates, the parallel rule is H1 ("BEGIN mode active on a TVM compute"). See the HP 12C guide for the equivalent g END fix.

Frequently asked questions

Does BGN affect non-annuity TVM problems? Yes. The BA II Plus does not distinguish between annuity and single-sum problems for the purpose of the BGN setting. A single-payment Present Value (PV) compute with BGN on is treated as if the payment occurs at the start of the period.

Why does BGN persist through power-off? Because the BA II Plus stores it in nonvolatile memory. The same is true for Periods per Year, decimal places, and the Chain vs Algebraic Order mode. The only way to clear all of them is 2nd then RESET.

Can I just ignore the annunciator and trust myself to remember? Most candidates can not, especially under exam-room time pressure. Building the habit during practice (always set END before each TVM compute, always check the annunciator) is the cheaper path.

Does Charterly auto-switch to END for me? No. Charterly never silently changes your inputs or settings. The warning surfaces; the keystroke fix is on the user. This is by design (AGENTS section 7).

Where can I see all the calculator mistakes Charterly tracks? The twelve CFA calculator mistakes page lists all of them across both devices.