13 Common Types Of Invoices Every Small Business Should Know

Mastering the art of invoicing is more than just sending out bills — it’s the backbone of your small business. Without smooth cash flow and accurate financial records, everything falls apart faster than you can say “accounts payable.”

By understanding the most common types of invoices, you can turn that chaotic pile of bills and financial documents into a well-organized system. Here is how to do just that (including helpful tips on how to choose the right invoice for each situation).

Quick overview of different types of invoices (and when to use each)

• Pro forma invoices provide a quote or estimate before a sale
• Sales invoices request payment after delivering goods or services
• Overdue invoices remind clients about late payments (and the fees they may incur)
• Consolidated invoices combine multiple invoices into one
• Retainer invoices bill for recurring services not yet performed
• Interim invoices bill for work on a milestone basis
• Timesheet invoices bill based on tracked hours
• Final invoices are simply the last bill of a project
• Credit memos document refunds or invoice reductions
• Debit memos document additional charges or invoice increases
• Mixed invoices apply both credit and debit notes together
• Commercial invoices detail goods sold internationally
• Recurring invoices bill for repeated services or subscriptions

One-time invoices

Whether it’s a freelance gig, a special order, or a unique service, one-time invoices are perfect for capturing your standalone jobs. Companies and contractors often turn to these invoices when they need to bill for something outside their regular offerings.

But, creating and sending one-time invoices can sometimes be a hassle. You might forget to include important details, leading to delayed payment. It’s an easy fix, though!

Set up an invoice template specifically for one-time invoices that includes all the necessary fields — like a detailed description of the service or product, the date, and payment terms. Try using invoicing software to automate and track these (even better if it integrates with your favorite timesheet app). 

1. Pro forma invoice (provides an estimate)

Before you deliver goods or services, you deliver a pro forma invoice. It’s a preliminary bill outlining the expected costs and terms of the transaction, so you and your client are on the same page. And if you’re not, you can make changes before the work starts.

Include the following on your pro forma invoice:

• Detailed description of the goods/services you’ll provide
• Estimated cost of the goods or services
• Delivery date or project timeline

2. Sales invoice (aka a ‘regular’ invoice)

Once the work is complete, you can go ahead and send off a regular/sales/standard invoice (whatever you want to call it).

This invoice is a legal document recording the financial transaction between the seller and the buyer. Sales invoices allow you to maintain accurate financial records, which is vital if any disputes over payment terms arise.

Include the following on your sales invoice:

• Your billing information
• Your buyer’s billing information
• Relevant contact information
• A unique invoice number
• Invoice date
• Description of goods/services (quantity/price per item)
• Total amount due
• Payment terms (like any late fees or the payment due date) 

3. Overdue invoice (aka ‘past due invoice’)

Nobody wants to send an overdue invoice because their initial invoice wasn’t paid on time. But it’s the reality of doing business. Unfortunately, overdue invoices can impact your business’s cash flow and overall financial health, so sending payment reminders is important. 

You should first address the problem by sending a polite reminder to your client — maybe there’s an invoicing error you can easily fix. If they continue ghosting you, apply the late fees outlined in your initial payment terms to your overdue invoice.

This can encourage them to handle things, but if not, more formal actions like involving a collection agency or pursuing legal action might be necessary.

4. Consolidated invoice (combines many invoices)

Make things easier for everyone and combine multiple invoices into one, especially when dealing with repeat customers. This benefits both you and your client (which will strengthen your relationship).

In your case, you’re reducing administrative overhead and the chance for errors. On the client’s side, a single invoice makes it easier to track their expenses and manage payments. Both sides have better bookkeeping, and you don’t have to request payment constantly!

Long-term project or retainer invoices

If you’re engaged in ongoing work or have recurring services, this type of invoice is your go-to. Whether you’re working on a project that stretches out over weeks or months, or you have a client on a regular retainer, you’re going to choose from one of these invoices.

Long-term work requires you to accurately track your hours worked, maintain consistent billing cycles, and make any billing adjustments due to changes in project scope. To keep everything under control, use time-tracking tools (did someone say Toggl Track?) for hourly work. See if you can set up automated recurring invoices if your billing is consistent each cycle.

And always, always communicate clearly with your client about any changes in the project or billing. Transparency is key to avoiding disputes and fostering healthy relationships. 

5. Retainer invoice (for ongoing relationships)

When you have a long-term business relationship with a client, especially if you offer different services each month, sending invoices at regular intervals is smart. Clients may be willing to pay you a fixed fee upfront for future services rather than dealing with multiple invoices. 

Freelancers commonly work with retainer invoices on a monthly schedule. This can help you build stronger relationships with your clients, as they foster a sense of ongoing partnership.

6. Interim invoice (for expensive, long projects)

If you have a large project and need a continuous cash flow, you can bill your client at different project milestones with an interim invoice. Unlike final invoices, you’ll issue interim invoices periodically—often monthly or at predefined project stages—to reflect the work you’ve completed up to that point. 

Breaking down the billing process into smaller, manageable increments mitigates any financial risk and ensures you and your client are happy. Interim invoices keep both parties aligned on project progress and costs.

Your client doesn’t have to hand over a giant sum of cash in one go, and you don’t have to worry about not getting paid until the project finishes.

7. Timesheet invoice (tracks hourly work)

If you work in an industry like consulting, legal, or marketing, you likely bill by the hour. (And ideally, you’ll use a billable hours tracker to stay organized.) Timesheet invoices detail the billable hours you’ve worked, breaking down your hours or even minutes spent on specific tasks or projects. 

Imagine you own a marketing agency where each team member logs their hours on various client campaigns, from brainstorming sessions to content creation.

At the end of the billing cycle, a timesheet invoice is generated — listing each employee’s hours, the tasks they performed, and the corresponding rates. This transparency isn’t just best for invoicing hourly work; it also builds trust with clients, who can see exactly where their investment is going. 

8. Final invoice (summarizes entire projects)

When you’ve come to the end of a major project, you tie up all the financial loose ends with a final invoice. This comprehensive bill summarizes and outlines every aspect of your completed work—from initial consultations to final deliverables. 

It combines all those earlier interim invoices, adjustments, and outstanding balances. This gives you and your client a clear and concise overview of the financial transaction. Like many other invoice payments, this creates trust and transparency between both parties. 

Invoice memos for correcting previous invoices

Hey, mistakes happen, and if they happen to you, you likely need to issue a credit or debit invoice memo. These invoice formats correct errors in previous invoices, like if you overcharged or undercharged a client. Think of them as the “Oops, let’s fix that!” of the invoicing world.

Invoice memos come with their own set of confusions, like whether you need a credit or debit memo or both. You also need to remember to reference the original invoice you’re amending.

We can’t stress how important communication is here. Make sure your client understands why they’re receiving the memo, double-check your numbers, and always tie it back to the initial invoice. 

9. Credit memo (offers a refund/discount)

If you’ve ever sent an invoice only to realize you charged your client too much, the situation can be fixed with a credit invoice. This adjusts previous amounts to ensure the mistake is fixed and everything is accurate and fair. Credit notes outline the amount you’re crediting back to the client, which reduces the total they owe and keeps your accounting neat.

10. Debit memo (increases amounts owed)

Debit notes are the opposite of credit notes. You use them to increase the amount your client owes you. Maybe you forgot to include some additional services in the original invoice, or perhaps an error needs correcting. It’s ​​a simple document outlining the extra charges and ensuring everything is accurate and up-to-date. 

11. Mixed invoice (simplifies complex adjustments)

You can send a mixed invoice rather than separate documents if you need to credit and debit a client in one go. Maybe you overcharged for one service but forgot to bill for another (hey, things happen). Just as you might send consolidated invoices to make everyone’s lives easier, the same idea applies to mixed invoices.

Other miscellaneous types of invoices

These last two invoices are unique — commercial invoices are used in international trade, and recurring invoices are common for subscription-based services. You need to maintain accuracy to avoid any customs delays and stay on top of any changes in subscription plans. Meticulous record-keeping is your best friend for these two different invoices.

12. Commercial invoice (for international trade)

You’ll need a commercial invoice for customs and tax purposes if you’re conducting international trade. These are more complex than others, as their function deals with cross-border trade.

13. Recurring invoice (for subscription-based services)

Recurring invoices automate the billing process, ensuring clients are charged consistently and on time for ongoing services. This saves you a ton of administrative hassle and promises a steady cash flow. 

Service providers operating on a subscription-based model typically deal with recurring invoices. They’re a great way to maintain strong, long-term client relationships by providing an easy and predictable billing experience.

Overcoming common invoicing challenges

The invoicing process isn’t always a breeze, and adding more tedious tasks to your workflow is the last thing you need.

Let’s tackle the most common invoicing challenges head-on and explore practical solutions:

• ⏰ Late payments: Implement clear payment terms at the beginning of the client relationship and use automated reminders as a gentle nudge.
• ✏️ Invoicing errors: Use invoicing software to automate calculations and reduce manual input.
• 🤯 Managing multiple client accounts: Centralize account management with a dedicated invoicing system for electronic invoices.
• 🌊 Cash flow management: Send invoices promptly. Consider retainer or interim invoicing and track payments closely.

Using Toggl Track for invoicing

Busy business owners and professionals should focus on delivering services instead of managing timesheets and invoices. This is easier said than done, which is why tools like Toggl Track are recommended to streamline billing efficiently and accurately. 

Simply take your weekly report and generate a digital invoice directly from that data. Customize it, download it, and it’s ready to send! It is that easy. Don’t believe us? Create a free Toggl Track account and see for yourself.