From Excel to ERP: A Migration Guide Without Drama

If you run your invoicing on Excel, its limits often appear as the workload grows: a gap in your numbering, an invoice you cannot find, or a quarter that does not add up.

This guide walks you through the migration process, from preparing and cleaning your data to reviewing it before issuing your first invoice in the new system.

Why Excel stops working

Excel is an extraordinary tool. But it is not an invoicing system. And the difference matters when:

Your volume grows. 10 invoices a month in Excel are manageable. 50 are a nightmare of copy-paste, broken formulas, and files that weigh 15 MB.

The tax office asks for something. If you receive an enquiry, you need to find every invoice for a specific quarter, with complete tax data. Preparation and validation time depends on the volume and quality of the source data.

You make mistakes. Manual invoicing is the leading cause of tax errors among freelancers. A miscalculated VAT, a missing withholding, a duplicate invoice number. Excel does not warn you.

Verifactu arrives. Electronic invoicing will be mandatory in Spain. Excel cannot generate electronic invoices or communicate with the AEAT. When Verifactu takes effect, you will have to migrate regardless.

Before migrating: prepare your data

The migration is only as good as the data you import. Prepare and clean your spreadsheets before starting an import.

1. Client list

Create a sheet with all your active clients. Minimum data per client:

If you have clients scattered across multiple sheets or folders, now is the time to consolidate them into one cleaned list you can use during review.

2. Product or service catalog

If you always invoice the same items (consulting hours, web design, monthly maintenance), create a list:

• Service/product name
• Unit price before tax
• Applicable VAT rate (21%, 10%, 4%, exempt)
• Unit of measurement (hour, unit, project)

3. Current year invoices

Export your invoices for the current year. At minimum you need:

• Invoice number
• Issue date
• Client (name + tax ID)
• Taxable base
• VAT
• Income tax withholding (if applicable)
• Total
• Status (paid/pending)

4. Current numbering

Note your last issued invoice number. The ERP will continue from there. If your last number is 2026-023, the ERP will start at 2026-024.

Step by step: migration in 5 phases

Phase 1: Create account and configure tax profile

Create your ERP account. Configure:

• Your business/freelancer details (name, tax ID, address)
• Tax classification
• VAT regime
• Income tax withholding (if applicable)
• Invoice logo
• Invoice series and starting number

This configuration is done once and applies to all future invoices. If your tax situation changes, you update it here.

Phase 2: Review client records

Use the cleaned client list as a checklist rather than assuming a generic client CSV import. Check that tax IDs are correct and there are no duplicates.

Add or review client records in a controlled batch, confirming each record before you continue.

Phase 3: Import products/services

Start Frihet’s product CSV import yourself with the cleaned catalog. Review the mapped columns and product rows before confirming. If you have a defined catalog, import products with prices and VAT rates. If you invoice custom services each time, you can skip this step and create line items on the fly.

Phase 4: Import invoice history

Start the invoice import wizard by uploading the document. Frihet uses OCR, then shows a preview that you can edit before you confirm. This step is optional but recommended. Importing current-year invoices lets you:

• Have your complete invoicing history in one place
• See confirmed imported data on the financial dashboard
• Include pre-migration data in quarterly VAT calculations

If you skip the history import, nothing terrible happens. The reports for your first ERP quarter will simply reflect only invoices issued after the migration.

Phase 5: Issue your first invoice

Create a test invoice. Verify that:

If everything checks out, you are invoicing with an ERP. That is it.

The 3 most common migration mistakes

Running both systems in parallel. The biggest mistake is continuing to use Excel “just in case” after migrating. If you invoice in both places, you end up with duplicate numbering, inconsistent data, and double the work. Pick a cutoff date and from that point on, ERP only.

Not verifying numbering. Before issuing the first invoice in the ERP, confirm the next number is correct. A gap or duplicate in numbering is one of the first things the tax office checks.

Preparing source data. Inventory and clean duplicate clients, incorrect tax IDs, and invoices with incomplete data in Excel before the cutoff. Use only the cleaned product catalog for the user-started CSV import. Use the client list as a checklist rather than assuming clients are imported into the ERP. For invoice documents, use the upload and OCR wizard, review and edit the preview, then confirm.

What you gain by migrating

The main differences between invoicing with Excel and invoicing with an ERP are in the workflow:

Time. An ERP can reduce repeated steps such as looking up client data, copying a template, calculating VAT, generating a PDF, and sending an email. The time saved depends on your volume, source data, and workflow.

Reviewable calculations. VAT is calculated automatically. Review numbering and auto-filled client data before issuing. Income tax withholding is applied when appropriate. Automation does not remove the need for human checks.

Visibility. You open the dashboard and see how much you have invoiced, how much you are owed, how much you owe the tax office this quarter. With Excel, that information requires cross-referencing multiple sheets and hoping the formulas are correct.

Compliance. When Verifactu arrives, your ERP will generate electronic invoices and communicate with the AEAT without you having to do anything additional. With Excel, that day will be a serious problem.

Migrating to Frihet

Frihet supports user-started CSV import for products. Prepare and clean the file, review the mapped data, and confirm before importing. Invoice documents use the upload and OCR wizard with preview, edit, and confirm steps. Guided tax configuration. The dashboard reflects data after it is confirmed.

The free plan gives you 999 invoices per month with no time limit. Enough to migrate, test with your real workflow, and decide if it works for you before paying anything.

If you have been telling yourself for years that “someday” you will stop using Excel, start by cleaning the source data and choosing a cutoff date. Review and confirm each supported import before issuing from the new system.