How to Build a £100,000 Investment Portfolio from Scratch

Building a substantial investment portfolio from scratch is one of the most consequential financial decisions you will make. Get the early decisions right — particularly the allocation and the wrapper — and you give yourself an excellent foundation. Make avoidable structural mistakes at the start, and you may pay for them in excess costs, suboptimal tax treatment, or inappropriate risk for decades.

This guide is aimed at investors who have approximately £100,000 to invest — whether as a lump sum from a bonus, a property sale, an inheritance, or accumulated savings — and who want a clear framework for building a portfolio that is appropriate, efficient, and sustainable.

Start with the Allocation Decision

Before you consider a single fund or platform, the most important question is: what is the portfolio actually for?

The answer determines almost everything else:

Long-term wealth accumulation (10+ years, no near-term need for income): A growth-oriented portfolio heavily weighted toward global equities is appropriate. Expect short-term volatility but superior long-run return.

Balanced growth and income (medium-term, some income wanted): A balanced allocation of 50–60% equities and 40–50% bonds and income-generating assets.

Capital preservation with modest growth (shorter horizon or limited risk appetite): A conservative allocation with minimal equity exposure, focused on protecting the real value of capital against inflation.

Retirement income-focused: A mix of income-generating equities, bonds, and real assets designed to fund regular withdrawals without depleting capital.

Being honest about your objective and time horizon at this stage prevents the most common mistake: choosing a portfolio that is either too conservative (generates insufficient growth) or too aggressive (you sell in a panic during a downturn).

Core Holdings: Building Blocks

For most investors, the most effective approach is to build from a small number of broadly diversified, low-cost core holdings:

Global equity tracker ETF. A single fund tracking the FTSE All-World Index (covering approximately 4,000 companies across developed and emerging markets) or the MSCI World Index (developed markets only) provides instant exposure to global equity markets. Cost: typically 0.10–0.22% per year. This single holding provides more diversification than most actively managed portfolios.

Global aggregate bond ETF or government bond ETF. A broad bond fund covering global investment-grade bonds, or specifically government bonds from the UK, US, and eurozone, provides the fixed income component. Duration (sensitivity to interest rates) and credit quality are key considerations given where you are in the rate cycle.

These two holdings — global equity and global bonds — form a complete, diversified, low-cost portfolio that most active managers fail to beat over 10 years. Everything else is a satellite position.

Satellite additions might include:

• A global real estate ETF (REITS) for property exposure and income
• An emerging market equity ETF for higher-growth market exposure
• A thematic ETF for a specific structural trend (AI, energy transition)
• A commodity ETF or gold ETC for inflation hedging
• A short-duration bond or money market fund for liquidity

For a £100,000 portfolio, keeping satellite positions small (5–10% per position, total satellite of 15–25%) maintains the cost efficiency and diversification of the core while allowing for expressed views.

The Wrapper Decision

For UK residents, the ISA (up to £20,000 per year) is the simplest and most tax-efficient wrapper for personal savings. The Lifetime ISA is available for those under 40 with specific first-property or retirement objectives. The SIPP (Self-Invested Personal Pension) provides additional tax relief on contributions but restricts access until the normal minimum pension age — currently 55, rising to 57 from 6 April 2028.

For internationally mobile investors — those who move between jurisdictions — the wrapper decision is more nuanced:

Offshore investment bond: The most flexible and widely applicable wrapper for globally mobile investors. Structured as a life assurance contract, it allows income and capital gains to accumulate without annual tax. Withdrawals (chargeable events) are taxed only when taken, and timing can often be managed to minimise tax impact. Available to investors regardless of current country of residence.

General Investment Account (GIA): A standard taxable brokerage account. No wrapper protection, but maximum flexibility — no contribution limits, no lock-ups, no wrapper charges. Income and capital gains are taxable in the relevant jurisdiction each year. Appropriate as the default when no tax-efficient wrapper is available or accessible, or for assets above the ISA/SIPP allowances.

Offshore platforms: For internationally mobile investors, specialist platforms (Novia Global, Transact International, Praemium International) provide access to a wide range of funds within an offshore bond or GIA structure, with regulatory protection in appropriate jurisdictions.

Platform and Account Provider Selection

The investment platform is where your portfolio actually lives. For UK residents with straightforward needs:

• Hargreaves Lansdown: Wide fund selection, excellent usability, higher platform charges for larger portfolios (cap available).
• AJ Bell: Broad selection, competitive charges, good for SIPP.
• Vanguard Direct: Extremely low cost, limited to Vanguard funds — ideal if you want the simplest possible setup.

For internationally mobile investors, UK-based platforms are often restricted to UK residents. Alternatives:

• Interactive Brokers: Global access, very competitive dealing costs, institutional-level trading capability. Less user-friendly than UK retail platforms.
• Saxo Bank: Global access, strong product range including ETFs, bonds, and currencies. Premium tier appropriate for portfolios of £100,000+.
• Novia Global / Transact International: Specialist offshore platforms for internationally mobile clients, wrapping investments inside offshore bonds or GIAs with appropriate regulatory oversight.

Understanding the Full Cost of Ownership

The cumulative effect of charges over 20 years is far greater than most investors appreciate. On a £100,000 portfolio:

• A total annual cost of 0.25% (cheap ETF portfolio, low-cost platform) leaves approximately 25% more after 20 years than a portfolio with total costs of 1.5% (active funds, full-service managed platform).
• For comparison at an assumed 6% gross annual return before fees: 0.25% cost → approximately £287,000 after 20 years; 1.5% cost → approximately £224,000 after 20 years. The difference is approximately £63,000 — more than half the original investment.

This does not mean the cheapest option is always the right one. Adviser value, wrapper efficiency, and portfolio appropriateness all matter. But charges should always be understood in full and compared explicitly.

The components of total cost:

• Platform / custodian charge: Typically 0.15–0.40% per year, often with a cap for larger portfolios.
• Fund charges (OCF): The annual cost of each fund, expressed as a percentage. Passive ETFs: 0.05–0.22%. Active funds: 0.45–1.5%.
• Transaction costs: Dealing charges for buying and selling funds. Some platforms offer free ETF trading; others charge £10–15 per deal.
• Advisory fees: If using a financial adviser, their fee (typically 0.5–1.0% per year on assets under advice, or a fixed annual retainer) is separate and additional.
• Wrapper charges: Offshore bond structures may have annual policy charges, administration fees, and early surrender penalties.

Getting Started: Deployment Strategy

Once the allocation, wrapper, and platform decisions are made, the final question is how to deploy the capital.

Option 1: Full immediate deployment. Statistically, this outperforms phased investing approximately two-thirds of the time, because equity markets tend to rise over time. The risk is that you invest at a short-term peak and face an immediate drawdown.

Option 2: Phased deployment over 3–6 months. A reasonable middle ground. Transfer 25–30% immediately into the core holdings. Hold the remainder in a money market fund or short-term government bond ETF earning reasonable yield while you phase the balance in monthly. Fully invested within four to six months.

A practical rule: if you would be emotionally devastated by a 20% fall in the week after investing your full £100,000, phase the deployment. If you can genuinely tolerate that and understand that the long-run return is what matters, invest immediately.

The Annual Review

A well-constructed portfolio does not need constant attention. An annual review is sufficient for most investors. At the review, check:

• Has the allocation drifted? If equities have risen significantly, the equity weight may be above target. Rebalance if the drift exceeds 5–10%.
• Have the costs changed? Platform and fund charges can change. Check the total cost of ownership annually.
• Has your situation changed? Time horizon, income needs, risk tolerance, and tax position all evolve. The portfolio should evolve with them.
• Are the core holdings still appropriate? Most core ETF positions do not need to change. Review whether any satellite positions should be maintained, enlarged, or exited.

The annual review should take no more than one to two hours for a simple portfolio. If it is taking significantly longer, the portfolio is probably too complex.

How Global Investments Can Help

At Global Investments, we work with investors building substantial portfolios for the first time and with those who have existing portfolios that need rationalising or optimising. We can advise on the most appropriate allocation for your goals and time horizon, help you navigate the wrapper and platform options available to internationally mobile investors, and provide ongoing oversight and annual review.

Our independence means we have no commercial relationship with any platform or fund provider. Every recommendation is based on what is genuinely right for your circumstances.

Please note that all investments carry risk. The value of your investments can fall as well as rise, and you may receive back less than you invest. The examples in this guide are illustrative and do not guarantee future returns. Tax treatment depends on individual circumstances and may change. This guide is for information purposes only and does not constitute personalised financial advice. Always seek professional advice relevant to your specific situation.