What Is an Invoice and How to Create One

An invoice is a formal document that records a sale and requests payment from a customer. It shows what was supplied, how much is owed, and when the payment is due.

For businesses, invoices do more than ask for money. They create a clear payment record and help track income. They also support accurate bookkeeping, tax reporting, and professional communication with clients.

This guide answers the practical questions UK small business owners actually ask – what is an invoice, how do invoices work, what must one legally include, and how to write an invoice that gets paid quickly.

What Is an Invoice?

An invoice is a document, paper or electronic, that a seller sends to a customer to request payment for goods or services already provided. It sets out what was sold, at what price, and by when payment is due.

An invoice formalises the relationship between buyer and seller. It’s the seller’s formal payment request, and it becomes the buyer’s record of what they owe. 

Invoices can be issued in two formats:

• Physical invoices – printed and posted or handed over;
• Electronic invoices – sent by email or generated directly inside invoicing software.

Most merchants now generate invoices through invoicing software or accounting software rather than by hand, and many use automated invoicing to create and send bills the moment a job is marked complete, cutting admin time and reducing errors.

Electronic invoices have become the default for most UK small businesses, since they’re faster to produce, easier to track, and simpler to fold into digital record keeping.

How Does an Invoice Work?

Unlike a shop or restaurant bill, which is settled on the spot, an invoice works with a delay.  Goods or services are delivered first, and payment follows under agreed terms. 

The process generally runs like this:

• The business delivers the goods or completes the service.
• An invoice is issued, setting out the amount owed and the payment terms.
• Payment terms are agreed (or confirmed, if set out in a contract or quote) – for example, payment within 14 or 30 days.
• The customer processes payment by bank transfer, card, or another agreed method.
• The invoice is marked as paid, and both parties keep a record for their accounts.

Invoices are usually issued once a job is complete or goods have shipped, though they can also be issued upfront (deposit invoices) or on a schedule (recurring invoices). 

These documents can be sent by email, post, fax, or any other method a business has available. They are used for domestic transactions as well as cross-border trade, where a commercial invoice takes over much of the job.

Why Are Invoices Required and How Do Businesses Use Them?

Invoicing is a legal and operational necessity for almost every business.

Accounting and bookkeeping

Invoices are source documents for accounting and bookkeeping. They show when revenue is earned and help match payments to specific customers. This makes it easier to monitor unpaid invoices and manage cash flow.

Sales invoices feed into profit and loss reporting, while purchase invoices support the recording of business expenses. Together, they help accountants prepare accurate year-end accounts and check that financial records are complete.

Invoices also create an audit trail. This is important when a business needs to review past transactions or answer questions from an accountant. For VAT-registered businesses, invoices can also support VAT reporting and evidence of the tax charged or reclaimed.

Tax compliance

For UK businesses, invoices are the paper trail HMRC expects to see behind every sale and behind every VAT charge for VAT-registered businesses. 

From 6 April 2026, Making Tax Digital for Income Tax requires self-employed people and landlords with qualifying income above £50,000 to keep digital records. They’re also asked to submit quarterly updates, which makes consistent, well-formatted invoicing more important than ever for staying compliant.

Cash flow visibility

A stack of issued invoices tells you exactly when money should be landing in your account, which supports better business planning and forecasting.

In addition, invoices, referenced by invoice number, let you see at a glance what’s been billed, what’s outstanding, and who owes what. A consistent invoicing record further makes reconciliation easier and gives you the historical data to analyse trends and forecast future sales.

What Information Must an Invoice Include?

Whatever invoice template you use, HMRC expects a set of invoice requirements to appear on every invoice you issue. 

A good invoice should include:

• A clear label identifying it as an invoice
• The invoice date (issue date)
• A unique invoice number for record keeping and reference
• The business details of the seller, including name, address and, where applicable, VAT number
• The customer details – full name and address (and VAT number, if the customer is VAT-registered)
• A description of goods or services supplied, including quantity
• The date the goods or services were supplied, if different from the invoice date
• Unit costs and the total amount due
• Any applicable VAT on invoices – the VAT rate charged and the VAT amount payable, where the business is VAT-registered
• Payment terms, including the due date and accepted payment methods (bank transfer, card, and cash)
• Discounts, early payment incentives, or partial payment terms, if relevant
• Shipping costs and terms for goods invoices

Getting this list right the first time avoids the most common cause of invoice queries and payment delays – a customer sending it back because a detail is missing.

Types of Invoices and When To Use Each

Different invoice types suit different transactions. Here are the six most common invoice types UK businesses use.

Standard Invoice

A standard invoice records a one-off sale between a merchant and a customer and sets a due date for payment. 

Most freelancers, tradespeople and small retailers will use this as their default invoice template.

Commercial Invoice

Used for international shipments, a commercial invoice is generally required by customs officials and includes a detailed cost description. 

Since Brexit, any shipment moving through EU or UK customs procedures also needs an EORI number, so UK exporters should have theirs ready before goods leave the country. 

Commercial invoices typically spell out delivery terms, insurance arrangements, and any upfront payment required before final handover of goods.

Recurring Invoice

Recurring invoicing involves an invoice that is usually sent to a customer for goods or services delivered on a regular basis. These invoices typically provide for recurring payments. 

Subscriptions are good examples of these invoice types and can be sent out on a weekly, bi-weekly, monthly or annual basis, depending on the payment plan the customer has chosen. 

Pro Forma Invoice

A pro forma invoice is a “bill of sale” that is sent before delivery or shipment. 

It will typically include the delivery items, shipping weight, and transport charges, excluding the cross-border fees for sellers.

These types of invoices are generally used for international shipments and can be used at customs. Its terms of sale can usually be subject to change. 

VAT Invoice

A VAT invoice is used by VAT-registered businesses to charge VAT on a sale or to allow a VAT-registered customer to reclaim VAT on a purchase. 

As of 2026, UK businesses must register for VAT once their taxable turnover passes £90,000in any rolling 12-month period, and VAT invoices must show the VAT rate and amount separately from the net price.

Electronic Invoice (E-Invoice)

Merchants who seek to request payment from their customers can also do so via e-invoices, which are considered final invoices for services delivered. 

Created automatically through specific invoicing or accounting software, electronic invoicing is a streamlined way to control a business’s incoming funds through internal control invoices.

Invoice vs Receipt: What Is the Difference?

Invoices and receipts are often confused, but they serve different purposes:

• An invoice is issued before payment – it’s a request for money owed.
• A receipt is issued after payment – it’s confirmation that money has already changed hands.

Accounting-wise, an invoice is closely linked to a business’s account and creates an entry in accounts receivable (money owed to you) or accounts payable (money you owe), while a receipt closes that entry out once payment clears. 

For the customer, an invoice is something to action, while a receipt is something to file for expenses, warranties, or tax purposes. 

Many UK businesses issue both an invoice to request payment and a receipt or a “paid” stamp on that same invoice once funds arrive.

What Are the Legal Implications of an Invoice?

In the UK, the legal implications of an invoice include:

Late payment is a real and growing problem for UK small firms.

The Small Business Commissioner estimates that businesses are collectively owed around £26 billion in overdue invoices at any given time, and that late payment contributes to roughly 14,000 business closures a year. 

How to Create an Invoice

Whether you’re writing your first invoice or refining your process, the steps are largely the same:

• Step 1: Choose an invoice format – Use a ready-made invoice template in your invoicing software, a spreadsheet template, or a Word or PDF template if you’re just starting out. A consistent template speeds up how to write an invoice each time and keeps your branding uniform.
  
• Step 2: Add the mandatory information – Include invoice number, invoice date, your business details, customer details, and a clear description of goods or services supplied.
  
• Step 3: Set your payment terms – State the due date plainly (for example, “payment due within 14 days”) and list accepted payment methods.
  
• Step 4: Apply taxes and discounts – Add VAT if you’re VAT-registered, and clearly show any discounts or early payment incentives.
  
• Step 5: Review before sending – Check totals, VAT calculations, and customer details for accuracy. A wrong figure or missing VAT number is one of the most common reasons invoices bounce back unpaid.

For UK sole traders and small businesses, tools like invoicing software built into your accounting platform can generate a compliant invoice template automatically. 

They can also calculate VAT for you and store every invoice for record-keeping and Making Tax Digital purposes.

How to Send an Invoice

Once an invoice is ready, you have several options for how to send an invoice to your customer:

• Email invoices – the most common method for UK small businesses, usually as a PDF attachment.
  
• Postal invoices – still used for some B2B or older-style customer relationships.
  
• Electronic invoicing systems – invoices generated and delivered directly through invoicing software, often with a built-in payment request.
  
• Automated invoicing software – schedules and sends recurring or milestone invoices without manual input.
  
• Payment collection methods – increasingly, invoices include a direct payment link so a customer can pay by card or bank transfer the moment they open it, shortening invoice processing times considerably.

In some cases, businesses use a combination of these options based on business type and customer preferences. 

How to Get Paid Faster With Invoices

Getting an invoice out the door is only half the job. Getting it paid on time is the part that protects your cash flow.

For UK SMEs, faster payment starts before the invoice is sent. Clear payment terms should be agreed before work begins. This removes uncertainty around the due date and gives the customer a clear payment obligation.

The payment deadline also matters. Many freelancers and small businesses find that 14-day terms work better than 30-day terms. A shorter window gives customers less time to delay, forget, or push the invoice down their priority list.

Payment reminders should be built into the process. Automated reminders sent before and after the due date reduce manual chasing. They also make follow-up feel consistent rather than reactive.

Customers should have more than one way to pay. Card payments and bank transfers make settlement easier. The fewer barriers a customer faces, the faster the invoice is likely to be paid.

Early payment incentives can also help. A small discount for payment within a shorter period can encourage faster action. This works best when the incentive is clearly stated on the invoice.

Businesses should also understand their rights on late payment. Under UK law, commercial invoices can qualify for statutory interest and a fixed compensation fee when they are overdue. Most businesses use this as a final option, but knowing the rule gives you more control.

Following these tips is incredibly important, especially given that 90% of UK businesses are facing payment delays.

Conclusion

An invoice is simply a formal request for payment, but it also does a lot of quiet, essential work behind the scenes. 

With UK late payments still costing small businesses billions of pounds a year, getting your invoicing process right isn’t just good admin. It’s one of the most effective things you can do to protect your cash flow. 

If you’d like a hand streamlining that process, myPOS Invoicing is built to make creating, sending and getting paid for your invoices as smooth as possible.

Frequently Asked Questions

How do I choose the right invoicing software for my SME?

Look for software that offers invoicing, payment tracking, VAT support, accounting integrations, and features that match your business size and budget.

Can I use free invoicing templates, or are paid solutions essential?

Yes, free templates are suitable for many small businesses. However, paid invoicing software can save time by automating invoices, reminders, and record-keeping.

What are the legal requirements for invoice content in the UK?

A UK invoice should include your business details, the customer’s information, a unique invoice number, invoice date, description of goods or services, amounts charged, and VAT details if you’re VAT registered.

How can I automate recurring invoices for subscription services?

Most invoicing software allows you to schedule recurring invoices at set intervals and send automatic payment reminders to customers.

What’s the best practice for chasing late payments effectively?

Send polite payment reminders before and after the due date, follow up promptly, keep communication professional, and clearly state any late payment terms.

Are there specific VAT rules for invoices I need to follow?

Yes. If you’re VAT registered, your invoices must include your VAT registration number, the VAT amount charged, the applicable VAT rate, and meet HMRC’s VAT invoicing requirements.