UK Promissory Note Template: Key Clauses for Startup & SME Loans

If you’re lending money to (or borrowing money through) your startup or small business, it’s tempting to keep things informal. After all, you probably trust the other party, and you just want to get the funds in and get moving.

But when repayment dates slip, memories get fuzzy, or the business hits a rough patch, “we’ll sort it out later” can quickly turn into a dispute.

That’s where a properly drafted promissory note can help. In this guide, we’ll explain what a promissory note is, when it’s useful, and what a UK promissory note template should include so your business is protected from day one.

We’ll also share a practical “sample promissory note” structure (in plain English) so you know what to ask for when you’re getting one drafted.

What Is A Promissory Note (And Why Do Businesses Use One)?

A promissory note is a written promise to repay a debt. In its simplest form, it’s a document where:

• the borrower promises to pay a specific amount of money, and
• the lender can rely on that written promise as evidence of the debt and the repayment terms.

In a startup/SME context, promissory notes often show up when:

• a founder lends money to their company to cover cash flow;
• a business borrows from friends/family or a private lender;
• one company lends to another company within a group; or
• a supplier, investor, or partner advances funds on agreed terms.

A promissory note is usually more straightforward than a long-form loan agreement, but it still needs to be legally clear. If you want the document to be enforceable, it should also reflect the basics of contract formation (offer, acceptance, consideration, and an intention to create legal relations).

It’s also worth noting there’s a difference between (1) a “promissory note” used as a simple IOU/contract and (2) a promissory note intended to operate as a negotiable instrument under the Bills of Exchange Act 1882. If you need the note to be transferable and enforceable like a bill of exchange, the wording and structure need to meet specific statutory requirements (for example, an unconditional promise in writing to pay a sum certain in money, to or to the order of a specified person or to bearer, payable on demand or at a fixed/determinable future time, and signed by the maker). If you’re not aiming for negotiability, you should still draft clearly - but you may not need (or want) the formal “to order/bearer” style language.

It’s also not just a “template exercise”. The legal and commercial risks (like default, insolvency, interest, security, and enforceability) can vary a lot depending on your situation - and some lending can raise regulatory issues (see below).

When Should A Startup Or SME Use A Promissory Note?

A promissory note can be a good fit when you want a clear written IOU without negotiating a lengthy facility agreement.

Common scenarios include:

1) Director Or Shareholder Loans To The Company

It’s very common for directors to inject funds when a business is growing (or when cash flow is tight). A promissory note can be used to document repayment and interest, but you’ll often want the terms to align with your broader arrangements around management and ownership (for example, your Shareholders Agreement if you have multiple shareholders).

In practice, many businesses prefer a dedicated loan agreement for director lending, especially where the sums are significant or where repayment is linked to future funding rounds. In that case, it can be more appropriate to use a Directors Loan Agreement rather than a basic promissory note.

2) Short-Term Working Capital Between Businesses

If you’re lending money to a limited company (whether it’s your own or another business), you’ll generally want:

• a clear repayment date (or clear triggers for repayment);
• default/interest consequences; and
• confirmation of who is legally liable (company, individual guarantor, or both).

3) Simple Private Lending To A Business

Sometimes a promissory note is used where a private lender (or a friend/family member) is helping the business get off the ground quickly.

Even if the relationship is friendly, you still want the terms written down. A promissory note can reduce misunderstandings and show that the parties agreed the key points upfront.

4) “Bridge” Funding While You Finalise Longer Documents

Startups often move fast. If you need funds now but a full suite of documents will take time, a promissory note can act as a temporary arrangement.

That said, if the loan is complex (security, drawdowns, covenants, multiple lenders), a promissory note template may be too lightweight, and a tailored loan agreement is usually the safer choice. If you’re looking for a more detailed approach, you may want to start from a Loan Agreement structure instead.

Promissory Note Template (UK): What Should It Include?

If you’re searching for a promissory note template, the key is to understand the clauses that make it commercially workable and legally enforceable in the real world.

Below is a practical checklist of what a promissory note should usually include for startup and SME loans in the UK. (Think of this as the building blocks of a “sample promissory note” rather than a one-size-fits-all template.)

1) Parties (Who Owes What To Whom)

You’ll want the full legal details of:

• Lender: name, address, and (if a company) company number and registered office.
• Borrower: same details as above.

This sounds basic, but it’s a common failure point. If the borrower is “the business” but you’ve written an individual’s name (or vice versa), enforcement becomes messy.

2) Principal Amount (How Much Is Being Borrowed)

The promissory note should clearly state the amount being loaned (the principal). If the money is advanced in multiple payments, you should specify whether:

• the promissory note covers all advances up to a cap; or
• each advance requires a separate note (or a clear schedule).

3) Issue Date And Term

Set out:

• the date the promissory note is signed (and ideally when the money is advanced); and
• the term (for example, repayable within 6 months, 12 months, or on demand).

“On demand” sounds simple, but it can create uncertainty if the borrower’s cash flow planning depends on a predictable repayment schedule. If you use “on demand”, be clear on how a demand is made (email, letter, etc.) and whether any notice period applies.

4) Repayment Terms (When And How Payment Is Made)

A strong promissory note template will spell out the mechanics, such as:

• repayment date(s);
• instalments (weekly/monthly), if relevant;
• bank account details for payment;
• whether early repayment is allowed and whether there’s any fee or interest adjustment; and
• how payments are applied (interest first, then principal, or vice versa).

This is where “template” documents often fall short. Your repayment structure should match how the business actually operates.

5) Interest (If Any) And How It’s Calculated

Not every promissory note charges interest, especially where a director is temporarily funding their own company. But if you do charge interest, it should state:

• the interest rate (fixed or variable);
• when interest starts accruing (from advance date, issue date, or another date);
• how interest is calculated (daily, monthly); and
• when interest is payable (monthly, on maturity, on demand).

If there’s a higher interest rate on default (a “default rate”), include that too, and make sure it’s commercially reasonable. Overly punitive terms can cause enforceability headaches.

6) Default And Late Payment Consequences

This is one of the most important parts of a promissory note for SMEs.

Your note should define what counts as a default, for example:

• missing a repayment;
• breaching a key obligation (like providing information or maintaining insurance, if relevant);
• insolvency events (administration, liquidation, inability to pay debts);
• unauthorised transfer of the borrower’s business/assets (depending on the deal).

It should then set out what happens if default occurs, such as:

• the lender can demand immediate repayment of the outstanding amount;
• default interest applies;
• the lender can recover reasonable enforcement costs; and
• the lender’s other legal rights are preserved.

7) Security And Guarantees (If The Lender Needs Extra Protection)

Many promissory notes are unsecured. That means if the borrower can’t pay, the lender may just be an unsecured creditor.

If the lender wants extra protection, you might consider:

• personal guarantee (for example, a director guaranteeing the company’s debt);
• security over assets (like a fixed charge over specific assets or a debenture); or
• retention/conditions tied to a wider commercial agreement.

Security and guarantees usually require additional documents beyond a basic promissory note, and the wording needs to be handled carefully (especially if you’re trying to enforce later). Also note: a guarantee generally needs to be in writing and signed by (or on behalf of) the guarantor to be enforceable under the Statute of Frauds 1677 - so don’t rely on a verbal promise or informal messages.

8) Assignment (Can The Lender Transfer The Debt?)

Sometimes lenders want the ability to sell or transfer the debt (for example, to another investor or entity). If that’s part of the commercial deal, the promissory note should deal with assignment.

Debt transfers can become technical quickly, so it’s worth understanding how a Deed of Assignment may fit into the broader picture.

9) Notices (How The Parties Communicate Formally)

Good “housekeeping” clauses reduce disputes. Include how formal notices must be served, for example:

• email address for notices;
• postal address;
• when notices are deemed received; and
• whether delivery/read receipts matter.

This becomes critical if the note is “repayable on demand” or if default is triggered by notice.

10) Governing Law And Jurisdiction

For UK businesses, you’ll generally specify the law of England and Wales (or Scotland / Northern Ireland, if that’s where you operate and want the agreement governed).

This clause helps avoid arguments about which country’s courts should decide the dispute.

11) Signatures (And Capacity To Sign)

The promissory note needs to be properly signed by the borrower (and any guarantor, if applicable). If the borrower is a company, you’ll also want to ensure the company signs in a valid way under UK company law.

If consideration is unclear (for example, where the note is issued after funds have already moved, or you’re varying/waiving rights without anything new in return), you may need to document the arrangement as a deed to avoid enforceability arguments. If you’re signing anything more formal as a deed (which can sometimes be relevant in debt arrangements), it’s worth following best practice for executing deeds so you don’t end up with a document that’s hard to enforce.

Common Promissory Note Template Mistakes (And How To Avoid Them)

Promissory notes look simple, which is exactly why businesses often underestimate the risk.

Here are common issues we see when people rely on a generic promissory note template without tailoring it.

Unclear Borrower Identity

If the borrower is a limited company, make sure the company is named correctly (including the company number). If it’s an individual, use their full legal name and address.

This matters even more when you’re dealing with group structures and multiple entities. If you’re planning a restructure or adding new shareholders, don’t forget how financing interacts with your constitutional documents like your Articles of Association.

No Real Repayment Mechanism

“Borrower will repay the lender ASAP” is not a repayment clause.

At minimum, you want dates, a schedule, or clear triggers (and what happens if those triggers don’t occur).

Default Provisions That Don’t Match Reality

If you define default too broadly, you can create unnecessary tension in the relationship. If you define default too narrowly, the lender may have limited options when repayment problems start.

The goal is to be commercially fair but clear.

Forgetting Insolvency Risk

For startups, insolvency risk is always part of the picture (even if everyone is optimistic). If the borrower becomes insolvent, an unsecured promissory note may leave the lender with very limited recovery options.

If the amount is meaningful, consider whether security, guarantees, or a more detailed loan agreement is appropriate.

Not Thinking About What Happens If The Relationship Changes

Imagine you lend money to a co-founder’s company, and six months later the co-founder exits or the business changes direction.

If the promissory note doesn’t deal with assignment, early repayment, and default triggers, you can be left negotiating under pressure. That’s why promissory notes should be drafted with the “future you” in mind, not just today’s cash injection.

How Do You Sign And Store A Promissory Note Properly?

A promissory note is only as useful as your ability to prove it exists, prove it was agreed, and prove the terms.

A few practical tips that help startups and SMEs:

Get The Signing Right

• If it’s a company borrower, ensure the right person signs with authority (and consider board approval if appropriate).
• If there’s a guarantor, make sure they sign too (and that the guarantee wording is clear and in writing).
• Avoid last-minute edits after signing. If terms change, document the change properly (not just “we agreed by text”).

Keep Clean Records

• Store a signed PDF in a secure folder with restricted access.
• Keep proof of the bank transfer/advance (and tie it to the note via reference).
• Track repayments against the schedule (so you can quickly identify late payment or default).

Make Sure Your Accounting Matches The Legal Paperwork

Promissory notes often sit alongside director loan accounts, related party transactions, and sometimes investor reporting. If your accounts say one thing and your promissory note says another, that can create confusion and risk later.

This article is general legal information only and isn’t tax, accounting or financial advice. If you’re unsure whether a promissory note is the right tool (or whether you need a more detailed loan agreement), it’s worth getting advice before funds move. Fixing documents after a dispute starts is always harder.

Regulatory Note: FCA / Consumer Credit Considerations

If lending is carried on “by way of business”, or the borrower is an individual/sole trader/partnership (rather than a limited company), UK financial services and consumer credit rules can be relevant. Whether authorisation or exemptions apply depends on the facts (including who is lending, who is borrowing, and the purpose of the loan). If there’s any doubt, get advice before money is advanced.

Key Takeaways

• A promissory note is a written promise to repay a debt, often used for simple startup and SME loans.
• A promissory note template is not one-size-fits-all - the repayment terms, default clauses, and parties must match your real commercial deal.
• Key clauses usually include the principal amount, repayment schedule or demand mechanism, interest (if any), default triggers, notices, governing law, and valid signatures.
• If you want the note to be a negotiable instrument, it needs to meet the Bills of Exchange Act 1882 requirements; if consideration is unclear, a deed may be more appropriate.
• If the lender needs stronger protection, you may need extra documents (like security or a guarantee). Guarantees generally need to be in writing and signed to be enforceable.
• Signing and recordkeeping matter: a clear paper trail (signed note + proof of funds + repayment tracking) can prevent disputes and support enforcement if things go wrong.

If you’d like help drafting or reviewing a promissory note for your business (or figuring out whether a loan agreement is the better option), you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.