1. Sending it late
The payment clock starts on the invoice date. A week’s delay in issuing adds a week to every step that follows. Invoice on completion — same day.
2. Sending it to the wrong person
Your contact approves; accounts payable pays. Get the accounts address at the start of the engagement.
3. Leaving off the purchase order number
With larger customers, an invoice without a PO is frequently rejected automatically and silently. Ask whether one is needed before you invoice, not after.
4. Vague line descriptions
“Services rendered — 2,400.00” cannot be approved without a conversation. Name the deliverable, the dates and the agreement it comes from.
5. No due date
“Payment on receipt” means nothing to a company that pays on the 25th. Print an actual date.
6. Reusing or skipping invoice numbers
Duplicates make reconciliation impossible; unexplained gaps invite questions in an audit. Never correct an invoice by editing and resending under the same number — credit it and reissue. See invoice numbering.
7. Applying tax before the discount
Tax is due on what the customer actually pays. Discount first, tax on the remainder. See how to add tax.
8. Rounding at the end instead of per line
Sum rounded line amounts. Rounding once at the end produces invoices that are a cent out — small, but it makes the customer check everything else.
9. Forgetting the deposit already paid
Show it as a deduction on the face of the invoice, with the date it was received. Relying on the customer to remember guarantees a query.
10. No payment details
Bank details or a payment link belong on the document, not only in the email. The document is what gets filed and forwarded.
11. Ambiguous currency
“$” is used by more than a dozen currencies. Name it — USD, CAD, AUD, SGD.
12. Introducing terms for the first time on the invoice
A late-payment charge that first appears on the invoice is generally unenforceable. Agree terms before the work.
13. Sending an editable document
A word processor or spreadsheet file can be altered, re-flows on the recipient’s machine and looks provisional. Send a PDF.
14. Not keeping a copy
Keep the PDF you sent, not just the figures. It is your record of exactly what you asked for.
15. Not following up
Most unpaid invoices are not refusals; they are documents that got filed and forgotten. A reminder a few days after the due date recovers the majority.
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The five-second check before you send
- Correct legal name and PO number
- Unused invoice number
- Real due date
- Line totals add to the subtotal, and tax is calculated after the discount
- Payment details and currency on the document
- Attached as a PDF
Invoice & Quotation Generator for AndroidConsistent documents, saved details, automatic totals.
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Questions
What is the most common invoicing mistake?
Sending late. Everything downstream of the invoice date moves with it, and it is entirely within your control.
How do I fix an invoice I have already sent?
Issue a credit note against the original, then a new invoice with the next number in your sequence. Do not edit and resend under the same number.
Why do customers query invoices?
Overwhelmingly because a line description is too vague to approve, a reference such as a PO number is missing, or the figures do not obviously add up.
Is it rude to chase an invoice?
No. It is administration, and accounts departments expect it. Keep it factual, keep it on a schedule, and attach the invoice again each time.
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