Calculate a Time Weighted Return Around a New Deposit

An account balance includes both investment performance and money moving in or out. Comparing the ending value with the opening value without adjusting for those cash flows can produce a misleading return. Time weighted performance separates periods around external cash flows and links their returns, reducing the influence of when the investor happened to add or remove money.

The example below uses exact values immediately before and after one deposit. It excludes fees, taxes and distributions to keep the reconciliation transparent. A production performance system needs a stated valuation frequency, cash flow timing policy and treatment of costs; this short exercise is not a claim of compliance with any professional reporting standard.

Split the period at the cash flow

An account starts at $10,000. Before a new deposit, it rises to $11,000. The first subperiod return is $1,000 divided by $10,000, or positive 10%. The investor then deposits $9,000, making the postdeposit value $20,000.

Over the second subperiod, the account falls to $18,000 with no further cash flows. That subperiod return is negative $2,000 divided by $20,000, or negative 10%. The deposit belongs between the subperiods. Counting it as a gain in the first period would turn saving into investment performance.

Link the two subperiod growth factors: 1.10 × 0.90 = 0.99. Subtract one to obtain a time weighted return of negative 1% for the full period. Adding positive 10% and negative 10% to get zero would ignore compounding. A fall after a gain is measured against a different balance.

Reconcile the dollars as a separate result

The investor supplied $19,000 in total, consisting of the original $10,000 plus the $9,000 deposit. The account finishes at $18,000, so its dollar result relative to contributions is negative $1,000. This is consistent with a negative 1% time weighted result even though dividing $1,000 by $19,000 gives a different percentage.

More money was exposed during the second, losing subperiod. A time weighted return describes the linked investment performance without weighting each period by the investor’s deposited capital. A money weighted calculation incorporates cash flow dates and amounts, so it addresses the investor’s funding experience instead.

The account’s final balance is also 80% higher than its original $10,000. Calling that an 80% investment return would be plainly wrong because it counts the $9,000 deposit as part of the gain. A rising account balance can therefore coexist with a negative investment result.

Timing and valuations determine what can be calculated

This example works because the portfolio is valued immediately before the deposit and the deposit amount is known. If you only have a beginning balance, an ending balance and a total of deposits with no dates, you cannot reconstruct the exact same subperiod calculation. Do not quietly invent a midpoint date or assume every cash flow arrived on the first day.

Approximation methods exist, but their assumptions should be named and their limitations understood. A result derived from monthly statements can differ from one using daily valuations around every external cash flow. The difference is not automatically evidence of poor investment performance; it may reflect a different measurement method.

Keep distributions and fees consistent

Cash received from an investment inside the account is not necessarily an external contribution. For example, a dividend paid into the account and retained there belongs to investment performance under a total account valuation approach. Treating it as new saving would distort the return. A withdrawal of that cash by the investor introduces a separate external flow.

Charges also require a clear convention. Returns before and after account fees answer different questions. If a benchmark is gross of a cost that the account return deducts, explain the mismatch instead of drawing an unsupported conclusion about skill. A performance label is useful only when the underlying calculation is comparable.

Use the workspace for compatible data

The Advanced Analytics workspace accepts supplied series after conventions are confirmed. Do not assume an adjusted price CSV is a complete account ledger. Prices alone do not include the investor’s deposits, withdrawals, cash holdings or all account charges. A correlation calculation from those prices does not calculate the investor’s personal return.

Keep a separate cash flow record with dates, amounts and the account values needed by your selected performance method. Use the account recovery example when explaining why additional saving can restore a balance without repairing the original investment’s loss.

Report the question beside the answer

A clear report can show ending value, total contributions, dollar gain or loss and the chosen performance measure as separate items. Avoid annualizing a short observation without showing the period or implying it represents a sustainable yearly result. If the data cannot support the method, say what is missing.

The most useful outcome is not a more favorable return percentage. It is a return that answers a defined question and can be reproduced from the records. That makes it easier to compare performance, understand the effect of saving and avoid changing the measurement method merely because the account’s recent experience was uncomfortable.