Unified Portfolio View: Why It's Harder Than It Sounds

The core problem: everything is different

Listed equities and illiquid assets differ in almost every dimension that matters for tracking — pricing (continuous vs periodic), income (predictable dividends vs irregular distributions), currency handling, corporate action treatment, tax rules, and how cost basis adjusts over time.

A system that handles one well often handles the others poorly. Most portfolio trackers are built around listed securities and bolt on property and private assets as an afterthought. The result: these assets either show up incorrectly or not at all.

The currency problem

Even a simple two-asset portfolio — a GBP investor holding UK and US equities — introduces currency complexity that most tools handle badly.

For US equities, the cost basis needs to reflect the GBP equivalent at the time of purchase (using the GBP/USD rate on the trade date), and current value needs to reflect today's rate. The return has two components: dollar-denominated price appreciation and the currency effect. A system that uses a single current FX rate for everything will be wrong for every foreign-currency historical cost basis — and for assets held over years through significant currency moves, the error can be substantial.

The return attribution problem

Once you have a unified view, the natural next question is: where is my return coming from? This requires consistent attribution across asset types:

• Realised gains attributed to the period when the gain was locked in, not when cash was received
• Unrealised gains estimated even where current value is itself an estimate
• Income separated from capital appreciation
• Currency effects separated from underlying asset performance

The honest NAV

A personal portfolio NAV has two components: the certain part (listed securities and cash, where prices are objective) and the estimated part (private assets and property, where "current value" is derived from your most recent valuation estimate).

A good portfolio tracker makes this distinction visible — it doesn't present a precise-looking number that implies the entire portfolio is marked to market when half of it is marked to your last guess.

Debt as a first-class object

Most portfolio trackers track assets. Very few track liabilities properly. But for investors with mortgaged properties or leveraged positions, debt is a critical part of the picture.

A property worth £500,000 with a £300,000 mortgage is not a £500,000 asset — it's a £200,000 equity position. Showing only the gross asset value systematically overstates both portfolio value and diversification. Tracking debt properly means recording the principal, interest rate, outstanding balance, and net equity position.

What a real unified view requires

• A shared valuation model that handles each asset type with appropriate logic
• FX conversion at transaction date for all historical costs
• A consistent return methodology — specifically money-weighted IRR — across all asset types
• Debt tracking showing net equity positions, not gross values
• Temporal consistency — the portfolio's value at any historical date reconstructable from the transaction history