Writing an invoice should take two minutes. For many freelancers and small business owners, it takes thirty—and they still forget something.
The result? Delayed payments, confused clients, and that awkward "can you resend with the correct details?" email.
Here's how to write invoices that are professional, complete, and actually get paid.
What Every Invoice Needs
A proper invoice includes these elements. Miss any of them, and you're creating problems.
1. Your Business Information
At the top of the invoice:
- Business name (or your name if sole proprietor)
- Address
- Phone number
- Email address
- Logo (optional but professional)
This tells the client exactly who's billing them and how to reach you with questions.
2. Client Information
Who you're billing:
- Client's name or company name
- Billing address
- Contact person (for larger companies)
- Client email (useful for your records)
For corporate clients, make sure you have the correct legal entity name. "Acme Corp" and "Acme Corporation LLC" are different entities, and wrong names delay payment.
3. Invoice Number
Every invoice needs a unique identifier. This is non-negotiable.
Good formats:
- INV-001, INV-002, INV-003 (sequential)
- INV-2024-001 (year prefix)
- 2024-12-001 (date-based)
Pick a system and stick with it. Inconsistent numbering looks unprofessional and makes tracking impossible.
4. Dates
Two dates matter:
- Invoice date — When you issued the invoice
- Due date — When payment is expected
Common payment terms:
- Due on Receipt — Pay immediately
- Net 15 — Due within 15 days of invoice date
- Net 30 — Due within 30 days of invoice date
If you don't specify a due date, the client will decide when to pay. That's rarely in your favor.
5. Line Items
The core of your invoice. For each item or service:
- Description of what you provided
- Quantity or hours
- Rate or unit price
- Line total
Bad example:
"Design work — $2,000"
Good example:
- Homepage design — 6 hours @ $150/hr — $900
- About page design — 4 hours @ $150/hr — $600
- Mobile responsive updates — 3.5 hours @ $150/hr — $500
Detailed line items prevent disputes. The client knows exactly what they're paying for.
6. Financial Summary
After line items, show:
- Subtotal — Sum of all line items
- Taxes — Sales tax if applicable (show rate and amount)
- Discounts — If any apply
- Total Due — The final amount, prominently displayed
Make the total impossible to miss. Bold it. Make it bigger. This is the number that matters.
7. Payment Instructions
Tell them exactly how to pay:
- Accepted payment methods
- Bank account details (for transfers)
- PayPal or Venmo information
- Payment link (if using online payments)
- Check mailing address
The easier you make it to pay, the faster you get paid. Consider adding QR codes for Venmo, PayPal, or Zelle—one scan and they're paying.
8. Notes and Terms (Optional but Helpful)
- Late payment penalties ("1.5% monthly fee on balances over 30 days")
- Early payment discount ("2% discount if paid within 10 days")
- Project-specific notes
- Thank you message
Step-by-Step: Writing Your Invoice
Step 1: Gather Your Information
Before opening your invoice template or software, collect:
- Client's correct billing name and address
- What you delivered (dates, descriptions, quantities)
- Agreed-upon rates
- Any purchase order numbers they provided
Step 2: Create the Invoice Header
Add your business info and the word "INVOICE" prominently at the top. Add your logo if you have one.
Step 3: Add Invoice Details
Generate (or look up) the next invoice number in your sequence. Add today's date as the invoice date. Calculate the due date based on your payment terms.
Step 4: Add Client Information
Enter the client's billing details. Double-check spelling of company names.
Step 5: List Line Items
Add each service or product. Be specific in descriptions. Calculate line totals.
Step 6: Calculate Totals
Sum line items for subtotal. Add applicable taxes. Apply any discounts. Display the total prominently.
Step 7: Add Payment Information
Include all payment options you accept. Make it easy for them to pay right now.
Step 8: Review and Send
Check for typos, math errors, and missing information. Save a copy for your records. Send to the client via email (PDF attachment is standard).
Common Invoice Mistakes
Avoid these:
- Missing invoice number — Makes tracking and reference impossible
- No due date — Invites indefinite payment delays
- Vague descriptions — "Services rendered" tells them nothing
- Wrong client details — Especially company legal names
- Math errors — Nothing undermines professionalism faster
- Missing contact info — They can't pay if they can't reach you with questions
- Sending too late — Invoice the day you complete work, not days or weeks later
Tips for Getting Paid Faster
Invoice Immediately
Send the invoice the same day you deliver the work. Every day you wait is another day before you're in their payment queue.
Make Payment Frictionless
Offer multiple payment methods. Include QR codes for mobile payment apps. Add a payment link if possible. Remove every barrier between "I should pay this" and "paid."
Use Shorter Payment Terms
Net 15 gets paid faster than Net 30. Due on Receipt gets paid fastest. Consider what's appropriate for your client relationship.
Follow Up on Due Date
If payment doesn't arrive by the due date, send a polite reminder immediately. Most late payments aren't malicious—people forget. A nudge often works.
Establish Terms Upfront
Discuss payment terms before starting work, not after. Include them in your contract or proposal. No surprises on the invoice.
Consider Early Payment Discounts
"2% off if paid within 10 days" can accelerate payment. Do the math—2% may be worth it for faster cash flow.
Invoice Formats: Which to Use?
The standard. Professional, non-editable, universally readable. This is what most clients expect.
Word/Excel
Works for simple invoices, but editable documents feel less professional. If you're just starting, fine. Upgrade to PDFs as you grow.
Online Invoice Links
Some invoicing software generates a web link where clients can view and pay. Convenient, but make sure you also have the invoice stored locally for your records.
When to Use Invoice Software
Manual invoicing works when you have a handful of clients. As volume grows, it becomes a time sink:
- Tracking invoice numbers manually leads to duplicates
- Calculating totals by hand invites errors
- Following up on payments requires checking spreadsheets
- Finding old invoices at tax time is painful
Dedicated invoicing software handles these automatically. The catch: most charge $15-30/month. That's $180-360/year, forever.
IronBase offers a different model: professional invoicing for a one-time $79 purchase. Automatic invoice numbers, tax calculations, payment tracking, PDF generation—no subscription. Your data stays on your computer, and the software works offline.
Key Takeaways
- Every invoice needs: your info, client info, invoice number, dates, line items, totals, and payment instructions
- Be specific in descriptions—vague line items invite disputes
- Invoice immediately upon completing work
- Make payment as easy as possible (multiple methods, QR codes, payment links)
- Set clear due dates—no due date means "pay whenever"
- Follow up the day payment is late—most delays aren't intentional
A well-written invoice takes minutes. It should take minutes. Get a system, use it consistently, and spend your time on work that actually matters.