Convertible Loan Notes: How They Work And Key UK Startup Risks

If you’re raising money for your startup, you’ve probably heard investors mention a convertible loan as a “quick and simple” way to get funding in.

And to be fair, a convertible loan can be a really practical tool - especially when you’re pre-revenue, still validating your product, or you simply don’t want to spend months negotiating a company valuation.

But “quick and simple” doesn’t mean “risk-free”. A poorly drafted convertible loan (often documented as a convertible loan note) can create headaches later, from unexpected dilution to repayment pressure at the worst possible time.

Let’s break down what convertible loans and convertible loan notes are, how they work in the UK, and what you should watch for before you sign anything.

What Is A Convertible Loan (And What Is A Convertible Loan Note)?

A convertible loan is funding provided to your company as a loan now, with the intention that it will convert into shares later (most commonly at your next equity fundraising round).

In other words, it starts life as debt, but it’s designed to become equity.

A convertible loan note is the legal document (or set of documents) that records the terms of that arrangement. So when people ask, “what is a convertible loan note?” or “what are convertible loan notes?”, the simplest answer is:

• the company receives money now as a loan; and
• the investor gets the right for that loan to convert into shares later on agreed terms.

Convertible loan notes are commonly used by:

• early-stage startups raising a pre-seed or bridge round
• companies that want to defer valuation discussions until a later priced round
• founders who need speed and flexibility (but still want legal clarity)

It’s worth noting that you’ll also see misspellings like “convertable loan note” and “convertable loan notes” online - they’re usually referring to the same thing.

How Do Convertible Loan Notes Work In Practice?

Although each deal is negotiated differently, most convertible loan notes follow a fairly standard shape.

1) The Investor Advances Funds As A Loan

Your company receives investment funds, but legally it’s treated as a loan. That means:

• there’s typically interest (even if it’s low)
• there’s usually a maturity date (a deadline when something must happen)
• the investor is technically a creditor until conversion

From your perspective, it’s crucial to remember that while everyone may be working towards conversion, if things go off-track the “loan” nature can matter a lot.

2) The Loan Converts Into Shares On A Trigger Event

The most common conversion trigger is a qualifying financing round - meaning you raise a priced equity round above a certain threshold (for example, £250,000+ or £1m+, depending on the deal).

When that trigger happens, the loan will convert into shares in the way set out in the note (for example, automatically, or at the investor’s election - it depends on the drafting).

3) The Investor Gets A Better Price Than New Investors

Convertible loan notes usually reward early risk-taking. This is typically done via:

• a discount (e.g. 15–25% off the price per share paid by new investors); and/or
• a valuation cap (a maximum valuation at which the note will convert, even if the new round valuation is higher)

This is one of the key commercial points to negotiate carefully. Discounts and caps sound straightforward, but they drive dilution outcomes, and the maths can surprise founders if you don’t model scenarios.

4) If There’s No Trigger Event, The Maturity Date Matters

If you don’t raise a priced round before the maturity date, the note will usually set out what happens next. Common outcomes include:

• repayment of the loan (sometimes with interest)
• conversion at a pre-agreed valuation or formula
• extension of the maturity date (with investor consent)

This is where founders can get squeezed: it’s hard to repay startup funding if cash is tight - and maturity dates have a habit of arriving at inconvenient moments.

If you’re documenting a convertible raise, it’s also worth making sure the basic contract elements are properly handled (offer, acceptance, clear terms, signatures). If you’re unsure, it helps to sense-check the fundamentals of what makes a contract legally binding before you rely on a document that could shape your cap table for years.

Why Do UK Startups Use Convertible Loans?

Convertible loans are popular for good reasons - especially in the early stages.

They Can Be Faster Than A Priced Equity Round

Agreeing a valuation early can take time (and energy you’d rather spend building). A convertible loan can reduce negotiation friction by pushing the valuation discussion to a later round when there’s more traction.

They Can Be Cheaper Upfront

A full equity round often involves more documents, more due diligence, and more back-and-forth. A convertible loan note can be lighter - as long as it’s still drafted properly and tailored to your deal.

They Can Bridge You To A Bigger Round

If you’re close to hitting milestones but need runway to get there, a convertible loan can act like a bridge: enough capital now to reach a priced round later.

Just remember: speed is only a benefit if you’re not creating future problems. If you’re taking money in now, it’s worth getting the right structure and documentation from day one - especially if multiple investors are involved. Many startups pair a convertible raise with a clear Founders Agreement so roles, vesting, decision-making and exits are agreed early, before outside money adds pressure.

Key Terms In Convertible Loan Notes (And Why They Matter)

Here are the terms that most often drive risk (and disagreement) in a convertible loan note.

Valuation Cap

A valuation cap sets the maximum valuation used for conversion. If your next round is at a higher valuation, the note still converts as if the company were valued at the cap (meaning the investor gets more shares).

What to watch for: a low cap can cause much heavier dilution than founders expect, particularly if you later raise at a strong valuation.

Discount Rate

A discount gives the noteholder a reduced share price compared to new money investors in the next round.

What to watch for: discounts can interact with other mechanics in some notes, so you’ll want to confirm how the discount works alongside any cap.

Interest

Interest may accrue and then convert into shares (rather than being paid in cash). This is common - and it increases dilution.

What to watch for: confirm whether interest is simple or compound, and whether it converts automatically or only in certain circumstances.

Maturity Date

This is the deadline for conversion or repayment (or renegotiation). It’s a pressure point.

What to watch for: what happens at maturity if there’s no priced round? Automatic repayment obligations (or investor options to demand repayment) can be risky.

Qualifying Financing

This defines what kind of fundraising triggers conversion. Notes often set a minimum fundraising amount to qualify.

What to watch for: if the threshold is too high, you might raise smaller rounds that don’t convert the note, leaving you with an ongoing debt position that can complicate later fundraising.

Conversion Shares And Rights

It’s not just “shares”. The note should specify what class of shares the loan converts into (often the same class issued in the qualifying round), and what rights attach to them.

What to watch for: if the note converts into a share class with enhanced rights (or if noteholders get additional rights on top), that can affect founder control and future investment negotiations. This is where a well-structured Shareholders Agreement can become important once you have external investors and need clear rules around voting, reserved matters and transfers.

Change Of Control / Exit Provisions

If your company is acquired before the next funding round, the note should say what happens. Typical options are:

• repayment (maybe with a multiple)
• conversion immediately before the sale
• the investor choosing whichever outcome is better

What to watch for: outcomes where investors can receive repayment and conversion benefits, or where large multiples make an exit far less attractive for founders (the exact position depends on the drafting).

What UK Startups Should Watch For Before Signing A Convertible Loan Note

A convertible loan can be founder-friendly - but only if it’s structured with your growth plan (and risk profile) in mind.

1) Don’t Treat It As “Not Really Debt”

It’s easy to think a convertible loan is basically equity in disguise. But legally, it’s still debt until conversion.

That means if the business struggles, a noteholder might have creditor rights that equity investors wouldn’t have.

Practical tip: be clear on whether the loan is secured or unsecured, and whether there are any enforcement rights, default interest, or acceleration clauses.

2) Check Your Company’s Constitutional And Share Issuance Rules

Even though conversion happens later, you’re effectively pre-agreeing the framework for issuing shares.

Issues can come up if:

• your articles/shareholder arrangements include pre-emption rights or consent requirements
• the board/shareholders haven’t approved the relevant authority to allot shares
• the conversion mechanics don’t match how your company actually operates

Practical tip: get your corporate documents aligned early. It’s much easier to tidy this up before the note is signed than during a rushed fundraising or just before completion of a round.

3) Be Careful With “Most Favoured Nation” Clauses

Some notes include an MFN clause, which can allow earlier investors to “opt in” to better terms you later offer to other noteholders.

This can be reasonable - but it can also make later fundraising harder, because every improvement may cascade across prior investors.

4) Model Dilution Early (Not After You’ve Spent The Money)

Founders are often surprised by the eventual dilution impact of:

• the cap
• the discount
• accrued interest converting into equity
• multiple notes issued at different times on different terms

Practical tip: run a few scenarios (best case / expected / worst case) and make sure you’re comfortable with the outcomes before committing.

5) Watch For UK Financial Promotions Issues

If you’re raising from UK investors, there may be restrictions on how you market the opportunity. The UK’s financial promotions regime can apply to the communication of “invitations or inducements” to engage in investment activity.

This is one of those areas where founders accidentally take risks by sending pitch materials widely without checking whether exemptions apply (for example, high net worth or sophisticated investor exemptions).

Practical tip: if you’re doing an outreach campaign, consider getting advice early - especially if you’re sending decks broadly or using online marketing to attract investors.

6) Make Sure The “Next Round” Paperwork Is Anticipated

Convertible notes are designed to convert during a priced round, but your next round will likely involve:

• subscription documents and warranties
• updated constitutional documents
• side letters or investor rights terms

It can help to document the headline commercial terms early in a Term Sheet, so everyone is aligned on what “conversion” will look like in practice.

7) Think About What Happens If You Need To Restructure Later

If your company pivots, merges, or restructures, the note terms can complicate things - especially if the investor’s consent is required for changes or if the conversion mechanics don’t fit the new structure.

For example, if you need to move obligations from one entity to another as part of a reorganisation, you may need a Deed of Novation (and noteholders may have approval rights).

That’s not a reason to avoid convertible loans - it’s just a reminder to keep flexibility in mind when negotiating the terms.

What Documents Do You Usually Need For A Convertible Loan?

The exact paperwork depends on your raise and investor group, but UK startups commonly use:

• Convertible Loan Note Instrument / Agreement (the main document)
• Board minutes and shareholder resolutions (approvals to enter into the note and future share allotment mechanics)
• Cap table updates (to model conversion outcomes and keep records clean)
• Disclosure letter / due diligence responses (if the raise is more formal)
• Founder and investor arrangements (often consolidated into a Shareholders Agreement once equity investors come in)

If you’re documenting the investment, it’s worth doing it properly rather than trying to patch together templates. The goal is not to make the document “long” - it’s to make it clear, internally consistent, and aligned with how your company actually works.

If the investor is asking you to use their form note, don’t panic - that’s common. Just make sure you review it carefully so you’re not agreeing to terms that don’t fit your fundraising plan or risk tolerance. If you want a dedicated service for documenting this kind of raise, a tailored Convertible Note package can help keep things moving while still protecting your business.

Key Takeaways

• A convertible loan is funding that starts as a loan and is intended to convert into shares later, usually at your next priced equity round.
• Convertible loan notes can be a faster way to raise money early, but they still create real legal and commercial obligations you need to understand.
• Key terms to negotiate (and model) include the valuation cap, discount, interest, maturity date, and what counts as a qualifying financing.
• Be careful about what happens if you don’t raise again before maturity - repayment obligations (or other maturity outcomes) can become a serious risk for early-stage startups, depending on the drafting.
• Make sure the note aligns with your corporate documents and approval processes, and think ahead to how conversion will work when you bring in equity investors.
• Don’t DIY a convertible loan note: the “standard” terms are where most founder pain comes from, and tailored drafting can save you expensive disputes later.

Note: This article is general information only and isn’t tax, accounting or financial advice. If you need advice on tax or accounting treatment (for example, how a note is treated in your accounts), speak to a qualified adviser.

If you’d like help setting up a convertible loan note (or reviewing one an investor has sent you), you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.