Invoice Payment Terms Net 30: Your Complete UK Law Guide

If you're running a business in the UK, you've likely encountered—or offered—invoice payment terms net 30. But what does "net 30" actually mean? And more importantly, what happens when a client doesn't pay by day 30? Understanding net 30 invoice payment terms under UK law isn't just about knowing the rules; it's about protecting your cash flow and your business's survival.

In 2026, the statutory interest rate for late payments sits at 12.5% (Bank of England base rate of 4.5% plus 8%), thanks to the Late Payment of Commercial Debts (Interest) Act 1998. This is your legal safeguard—but only if you understand how to use it.

What Does Net 30 Mean?

Net 30 is straightforward in theory: payment is due within 30 days of the invoice date. The word "net" means the full invoice amount, with no deductions or discounts applied (unless you've explicitly agreed otherwise). So if you invoice on 1 April, payment is due by 1 May.

In practice, "net 30" is the most common commercial payment term in the UK, particularly for B2B transactions. It gives clients a month to process the invoice, arrange payment, and handle cash flow—while you wait for money that's technically yours.

The Late Payment of Commercial Debts (Interest) Act 1998: Your Legal Right

This is the law that matters. The Late Payment of Commercial Debts (Interest) Act 1998 gives you a statutory right to charge interest on overdue invoices—automatically, without needing to ask.

Key points:

• Automatic right: You don't need a contract clause mentioning interest. The law grants it to you by default.
• Statutory rate: In April 2026, this is 12.5% per annum (8% + Bank of England base rate).
• Who's covered: Freelancers, sole traders, partnerships, and limited companies supplying goods or services to other businesses or public authorities.
• What triggers it: A debt becomes "due" when payment is due under the contract. For net 30 terms, that's day 31 onwards.
• Debt recovery costs: You can also claim "reasonable" costs incurred in pursuing the debt (solicitor letters, court fees, etc.).

The Act applies to net 30 invoice payment terms and all other commercial payment terms. There's no exemption for small businesses or startups on the other side of the transaction.

How Is Statutory Interest Calculated?

Understanding the math helps you know what you're owed.

Formula: (Invoice Amount × 12.5% × Days Overdue) ÷ 365

Example: Invoice for £10,000, net 30 terms, unpaid for 60 days (30 days overdue):

(£10,000 × 12.5% × 30) ÷ 365 = £102.74 in statutory interest

That might not sound like much on a small invoice, but on a £50,000 debt unpaid for 90 days, you're owed over £1,500 in interest alone. Multiply that across multiple overdue invoices, and the incentive for clients to pay on time becomes very real.

When Does Net 30 Start? Key Dates

This seems obvious, but it's where confusion creeps in:

• The contract determines the trigger date. For net 30 invoice payment terms, payment is typically due 30 days from the invoice date (not the delivery date, unless your contract specifies otherwise).
• Example: Invoice dated 15 April → Payment due 15 May → If unpaid on 16 May, statutory interest accrues from day 1 of being overdue.
• Weekends and bank holidays don't pause the clock. Day 30 is day 30, regardless.
• Your terms take precedence if they're clearer. If your invoice says "Payment due 15 May," use that date, not "net 30 days from invoice."

Always include the specific due date on your invoice to eliminate ambiguity. "Net 30 from invoice date" is less clear than "Due 15 May 2026."

Best Practices for UK Invoicing with Net 30 Terms

1. Be Explicit on Your Invoices

Don't rely on "net 30" alone. Write:

"Payment due: [specific date]" or "Net 30 days from invoice date (due [date])"

This removes room for negotiation or misunderstanding.

2. Reference Your Payment Terms on Your Invoice

Add a footer or statement: "Payment for invoices not received by the due date will accrue statutory interest at 12.5% per annum under the Late Payment of Commercial Debts (Interest) Act 1998."

It's not aggressive—it's informative. And it demonstrates that you understand your rights.

3. Invoice Immediately

The sooner you invoice, the sooner the net 30 clock starts. Don't wait weeks to send an invoice. Invoice on the day you deliver goods or services.

4. Track Due Dates Religiously

Use invoicing software (FreshBooks, Xero, Wave) that flags overdue invoices automatically. Don't manually chase payments; let the system remind you.

5. Send Polite Reminders Before Day 30

A friendly reminder email a few days before the due date prevents many late payments. Some clients are simply disorganized, not deliberately avoiding payment.

6. Follow Up on Day 1 of Overdue

Send a formal "Payment Now Due" letter on day 31 if unpaid. This isn't rude—it's professional. Include the due date, invoice number, amount, and a statement that statutory interest is now accruing.

What Happens If They Still Don't Pay?

You have options:

• Send a Statutory Demand: A formal notice claiming the debt plus interest and costs. If unpaid within 21 days, you can escalate to court.
• County Court Claim: For debts under £100,000, use the County Court (usually fast and inexpensive).
• Debt Collection Agency: Hand the debt to a professional collector (they take a cut, usually 15-25%).
• Small Claims Track: For debts under £10,000, courts handle these quickly with minimal formality.

The key: most businesses pay once they receive a formal demand letter. The statutory interest and costs reminder usually does the trick.

Common Pitfalls with Net 30 Payment Terms

Assuming "Net 30" is Industry Standard

It's common, but not universal. Some industries use net 60 or net 90. Always agree on payment terms in writing before you start work. If a client says "we pay net 30," confirm it in writing. If they don't agree, negotiate before invoicing.

Forgetting to Include Due Dates on Invoices

An invoice without a clear due date is unenforceable under the Late Payment Act. The clock for statutory interest won't start. Always specify.

Not Calculating or Claiming Statutory Interest

Many small businesses don't claim the interest they're legally owed. Don't leave money on the table. Calculate it, add it to your demand letter, and claim it.

Accepting "We'll Pay When We Can"

This is not a valid renegotiation of net 30 terms. Once terms are agreed, they're binding. If a client can't pay on time, they're accruing statutory interest. Be sympathetic but firm.

Is Net 30 Right for Your Business?

Net 30 works if:

• Your clients are established businesses with reliable payment practices.
• You have cash reserves to cover the 30-day gap.
• You're invoicing regularly (multiple invoices means steady cash flow).

Consider net 14 or net 7 if:

• You're a freelancer or solopreneur with tight cash flow.
• Your clients are startups or new businesses with poor payment histories.
• You're in a high-risk industry (construction, creative services).

Consider 50% upfront + 50% on net 30 if:

• Your project spans weeks or months.
• You need to buy materials or subcontract before getting paid.

The 2026 Statutory Interest Rate: What You Need to Know

The statutory interest rate changes when the Bank of England base rate moves. In April 2026, it's 4.5%, making the statutory rate 12.5%. If rates change, your future invoices will reflect the new rate automatically—you don't need to do anything.

This is why tracking the base rate matters. If it drops, your interest income drops too. Plan accordingly.

Practical Example: Net 30 in Action

You're a freelance web designer in Manchester. You invoice Acme Ltd on 1 April for a website redesign: £5,000, net 30 terms, due 1 May.

• 1 May: Invoice due. No payment received.
• 2 May: You send a friendly reminder.
• 8 May: Still unpaid. You send a formal payment demand letter, stating that statutory interest is now accruing at 12.5% per annum.
• 15 May: Payment received, but 15 days late. You calculate: (£5,000 × 12.5% × 15) ÷ 365 = £25.68 in statutory interest. You add this to your next invoice or send a separate invoice for the interest owed.
• You've been paid, and you've recovered interest on the late payment—all without legal action.

This is how the Late Payment Act works in practice. It's not punitive; it's corrective. It makes paying on time more attractive than paying late.

Summary: Invoice Payment Terms Net 30 Under UK Law

Net 30 is a fair, standard payment term that gives clients a month to pay while protecting your rights under the Late Payment of Commercial Debts (Interest) Act 1998. By invoicing clearly, tracking due dates, and claiming statutory interest when necessary, you can maintain healthy cash flow and encourage on-time payments.

The key takeaway: you have the law on your side. Use it. Don't be ashamed to invoice for interest on late payments—it's not unfair, it's business.