NAV File Format

PortBlend Docs Last updated 28 Jun 2026

What is a NAV file?

NAV stands for Net Asset Value. The term comes from the mutual fund industry, where it refers to the price per unit of a fund calculated at the end of each trading day. The same concept appears under different names in other areas — an equity curve in trading and strategy backtesting, a price series or index level when tracking a benchmark, and a portfolio value or unit value in wealth management.

A NAV series is a record of how something performed over time — one value per period, on a regular schedule.

That something can be almost anything:

The closing price of a stock, commodity, or bond — available from public data sources such as Yahoo Finance or Google Finance
A blended portfolio of multiple assets, where you have computed a combined value over time
The output of a rule-based strategy or equity curve exported from backtesting platforms like TradingView or QuantConnect

The periods can be daily, weekly, or monthly. PortBlend works with all three.

Note

For Systematic Traders:

Clean your file: Backtest exports from platforms like TradingView or MetaTrader often contain extra columns (such as trade IDs or transactional logs). Clean the file so it contains exactly two columns: the date/timestamp and the cumulative strategy equity (NAV) value.
Account for execution overhead: Ensure your uploaded NAV already factors in real-world trading costs—including slippage, brokerage commissions, and swap/overnight funding charges. Ignoring these overheads will result in artificially smooth equity curves, severely understating your historical drawdown depths and recovery timelines.
Use fixed-unit performance: Portfolio Blending normalizes series to base 100 at the start date. If your backtested strategy reinvests profits to scale up unit sizes over time (e.g., compounding from 10 units to 11 units), it will distort the blend and escalate latter-stage drawdowns in your results. To get clean portfolio blending metrics, ensure your uploaded NAV series reflects a fixed-unit allocation throughout the entire historical range.

A valid portfolio file contains:

A date column — representing the dates of the observations
A NAV column — representing the performance/price index values

Download the sample file to see a working example:

Download sample NAV CSV

General file requirements

Your file needs to meet these requirements before uploading:

Requirement	Detail
Format	CSV, TSV, TXT, and Excel (XLSX, XLS)
Columns	Up to 15 (extra columns are ignored; columns can be mapped manually)
Row order	Any order (automatically sorted chronologically in browser)
Duplicate dates	Not allowed
NAV values	Numeric only (currency symbols like $, €, £, ¥, ₹, currency codes like USD, EUR, commas, spaces, and % are cleaned automatically)
Minimum rows	2
Maximum rows	10,000

If your source data has extra columns, PortBlend will automatically extract the best matching Date and NAV columns, keeping only those 2 for local storage. Unrelated columns are safely discarded.

Accepted column names

PortBlend matches column names using the accepted aliases below. Matching is case-insensitive, so Date, DATE, and date all work.

Accepted date column names:

Name	Notes
date	Recommended
date_time
tradedate
trade_date
datetime
timestamp
period
week	For weekly series
month	For monthly series
observation_date	Used in FRED economic data exports
nav_date
nav date

Accepted NAV column names:

Name	Notes
nav	Recommended
nav_value
equity
cum_nav
cumnav
cumulative_nav
close	Accepted (used by FRED and many market data exports)
value
portfolio_value
close/last

If your column names are not in these lists, rename them before uploading. For files with exactly 2 columns, the non-date column is automatically used as NAV regardless of its name.

Accepted date formats

ISO format (YYYY-MM-DD) is recommended. Formats that share the same digit pattern — such as DD/MM/YYYY and MM/DD/YYYY — are resolved by inspecting the files row sequence (detecting which slot increments frequently). If automatic detection fails, or if columns cannot be mapped, the Format Assistant modal opens to let you choose columns and dates manually.

Verify file format inline

Paste a few rows from the top of your file to verify column names, date format, and NAV values before uploading.

CSV File Validator— paste up to 10 rows to check your file

Error messages

Too many rows

File '[filename]' has [N] data rows. Maximum allowed is 10000.

Trim the file to 10,000 rows or fewer. For long daily series, consider uploading the period most relevant to your analysis.

Missing or unrecognised column names

If no column matches any accepted date or NAV alias, the upload fails with a column error. Rename the columns to match the accepted names. For files with exactly 2 columns the non-date column is always treated as NAV automatically.

Non-numeric NAV values

Check for blank cells or header rows embedded in the middle of the file. PortBlend automatically handles formatting issues by stripping currency symbols, codes like USD/EUR, and spaces. Rows representing holidays (e.g. dot values . or N/A) or empty lines are skipped. Summary totals and footers near the bottom of the file are skipped gracefully.

Duplicate dates

The error message shows the duplicate date value. Find and remove or correct the duplicate row.

Date order

PortBlend automatically sorts all uploaded rows chronologically before saving. You do not need to pre-sort your file.