Invoice Attachments
docs101 allows you to upload file attachments to your invoices. Attachments can be included when sending the invoice via email — for example, terms & conditions, project specifications, or other supporting documents.
Attachments are only included in the email sent to your customer. They do not appear in the invoice PDF itself and are not embedded, linked, or referenced in the generated PDF document in any way. The invoice PDF always remains a standalone ZUGFeRD/Factur-X compliant document.
When to Use Attachments
Common use cases for invoice attachments:
- Terms & Conditions: Attach your general terms and conditions as a PDF
- Project Documentation: Include project specifications or scope documents
- Time Sheets: Attach time tracking reports or detailed breakdowns
- Delivery Notes: Include proof of delivery or shipping documents
- Contracts: Attach signed contracts or agreements referenced by the invoice
- Spreadsheets: Include detailed calculations or cost breakdowns
Supported File Formats
The following file types can be uploaded as attachments:
| Category | Formats | Extensions |
|---|---|---|
| Documents | .pdf | |
| Word Documents | Microsoft Word | .doc, .docx |
| Spreadsheets | Microsoft Excel | .xls, .xlsx |
| Images | JPEG, PNG | .jpg, .jpeg, .png |
| Text | Plain Text | .txt |
Each attachment can be a maximum of 5 MB. There is no limit on the number of attachments per invoice.
Uploading Attachments
Step-by-Step
- Open the invoice you want to add attachments to
- Navigate to the "Attachments" tab
- Upload files using one of two methods:
- Drag & Drop: Drag files directly into the upload area
- File Browser: Click the upload area to open the file browser and select files
- Wait for the upload to complete — a progress bar shows the upload status
- The attachment appears in the attachments table once uploaded
You can upload multiple files at once by selecting several files in the file browser or dragging multiple files into the upload area.
The invoice must be saved before you can upload attachments. If you are creating a new invoice, save it first, then switch to the Attachments tab.
Attachments Table
After uploading, each attachment is shown in a table with the following information:
| Column | Description |
|---|---|
| File Icon | Color-coded icon based on file type (red for PDF, blue for Word, green for Excel, purple for images) |
| File Name | The original name of the uploaded file |
| File Size | Size in human-readable format (KB or MB) |
| Type | The MIME type of the file |
| Uploaded | Date and time of upload |
| Actions | Delete button to remove the attachment |
A badge on the Attachments tab shows the total number of attachments.
Deleting Attachments
To remove an attachment:
- Go to the "Attachments" tab
- Click the delete button next to the attachment you want to remove
- Confirm the deletion in the dialog
Deleted attachments cannot be recovered. Make sure you have a copy of the file before deleting it.
Sending Invoices with Attachments
When you send an invoice that has attachments, the email dialog shows a list of all available attachments:
- Click "Send Invoice" on the invoice
- In the send dialog, you will see an Attachments section listing all uploaded files
- All attachments are selected by default — uncheck any you do not want to include
- Use the "Select All" / "Deselect All" buttons to quickly toggle all attachments
- The dialog shows how many attachments are selected
- Click "Send" to deliver the invoice with the selected attachments
The customer receives the invoice email with:
- The generated invoice PDF (always included)
- All selected file attachments
To be absolutely clear: Attachments are sent as separate files alongside the invoice PDF in the email. They are never part of the invoice PDF itself. The PDF remains an unmodified, ZUGFeRD/Factur-X compliant document. Your customer receives the attachments as additional files in the same email.
Email Deliverability and Attachments
Your invoice needs to reach your customer's inbox — that is the priority. Attachments can affect whether an email gets delivered or lands in spam. Here is what you should know to make good decisions.
Safe Choices
- PDF files are the safest attachment type. Email providers and spam filters treat them as standard business documents.
- Images (JPEG, PNG) and plain text files are also generally unproblematic.
- Keep total email size reasonable. While each attachment can be up to 5 MB, aim to keep the combined size of all attachments under 10 MB. Smaller emails are delivered more reliably and download faster for your customer.
What to Watch Out For
- Word and Excel files (
.doc,.docx,.xls,.xlsx) are more likely to trigger spam filters, especially if they contain macros. When possible, convert these to PDF before attaching. - Multiple large attachments increase the chance of delivery issues. If you need to send many files, consider combining them into a single PDF or sending supplementary documents separately.
- Unusual file names with special characters can occasionally cause problems. Use simple, descriptive names like
Terms-and-Conditions-2026.pdf.
When In Doubt
If an attachment is not essential for the invoice itself, consider sending it in a separate email. The invoice PDF is the document that matters most — everything else is supplementary. docs101 always includes the invoice PDF, and you choose which additional attachments to include in the send dialog.
Best Practices
- Use descriptive file names: Name your files clearly (e.g.,
Terms-and-Conditions-2026.pdf) so your customer can easily identify them - Prefer PDF format: PDFs are universally readable, preserve formatting, and have the best deliverability profile
- Review before sending: Check which attachments are selected in the send dialog before clicking Send
- Avoid sensitive data: Do not upload files containing passwords, personal identification numbers, or other sensitive information as email attachments
Reference Links
- Create & Send Invoice — Complete invoice creation and sending workflow
- Email Configuration — Setting up your email sender settings