Invoices are documents your customers and their accountants keep, and in many countries they must contain specific information. WHMCS lets you control the company details, numbering, PDF layout and even the template code. This guide covers the settings from simple to advanced.
Before you start
- Your legal company name, address and tax or VAT number.
- A logo image in PNG or JPG.
- Check local rules for invoice content and numbering with your accountant.
Company details and logo
- Go to Configuration → System Settings → General Settings → General.
- Set the Logo URL (or upload under Brand settings in newer versions).
- Fill in Pay To Text with company name, address, registration and VAT numbers, and bank details if you accept transfers.
- Save.
Invoice numbering
Open the Invoices tab:
- Sequential Paid Invoice Numbering – unpaid invoices act as proforma invoices with temporary numbers; only paid invoices get a gap-free sequence. Required in many EU countries.
- Sequential Invoice Number Format – for example
{YEAR}-{NUMBER}to restart numbering yearly-style references. - Next Paid Invoice Number – set the starting point when you migrate from another system.
PDF settings
- Enable PDF Invoices and Attach PDF Invoices to emails.
- PDF Paper Size – A4 or Letter depending on your market.
- PDF Font Family – choose a font that supports your languages (for non-Latin scripts pick a Unicode font such as DejaVu Sans).
- Store Client Data Snapshot – keeps the client's address as it was when the invoice was issued.
Invoice notes and terms
Add standard text such as payment terms or bank reference instructions in Invoices → Invoice Notes (or per invoice in the admin area). Tax-related wording such as reverse-charge notes can be added automatically by VAT settings; see tax and VAT.
Advanced: customise the PDF template
The PDF layout is generated by invoicepdf.tpl in your active client-area template folder (for example templates/twenty-one/invoicepdf.tpl). In a child theme, copy the file and edit it – it uses PHP with the TCPDF library to place text, tables and images. Typical changes: logo size, colours, extra footer text, hiding empty fields.
Test with an existing invoice using Download PDF after each change. Keep changes in your child theme so updates do not overwrite them; see theme customisation.
The online invoice page
The HTML invoice customers see in the client area is viewinvoice.tpl. Adjust it in the child theme in the same way if you want the online view to match the PDF.
Troubleshooting
- Logo missing on PDF: the logo URL is not reachable from the server, or uses an unsupported format. Use a local path or a PNG.
- Characters show as question marks: the PDF font lacks those characters; change the font.
- PDF blank after template edit: PHP error in
invoicepdf.tpl; restore the original and reapply changes carefully.