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If you manage a Horizon Europe project, audits probably feel a bit intimidating. But with good organisation and a clear method, preparing your costs and the supporting documentation behind them is much easier than it seems.
In this quick guide, we explain how to organise your cost documentation, which mistakes to avoid, and the best practices that help ensure audits run smoothly and without surprises.
What does it mean for a cost to “pass” an audit?
A cost is considered acceptable if it meets five key criteria:
- Eligible: allowed under the programme and linked to the project
- Documented: clear evidence exists (invoice, payslip, receipt)
- Traceable: the cost can be followed from the activity to the accounting records
- Consistent: it makes sense within the project and your organisation’s role
- Within the eligibility period: incurred and paid within the correct dates
Practical example:
A software invoice linked to a project activity, properly paid and recorded → 
passes the audit.
Critical cost categories: personnel and invoices
Personnel
To keep everything in order you must keep in file:
- Employment contract
- Payslips and proof of payment
- Signed timesheets reflecting hours worked
- Calculation of the hourly rate
Common mistake: completing timesheets months later or allocating hours incorrectly → risk of rejection.
Supplier invoices (for Travel, Equipment, Other Goods and Services, Subcontracting)
For supplier invoices, it is important to ensure that:
- Are issued in your organisation’s name
- Clearly describe what was purchased
- Are paid and within the eligibility period
- Are linked to a project activity
Common mistake: “miscellaneous services” with no clear link → auditors request clarification.
Traceability and accounting records
Traceability is one of the areas where auditors request the most documentation. Each cost should follow a clear logical trail:
Project activity → Internal approval → Original document (invoice, receipt, payslip) → Proper accounting entry → Consistent financial reporting
To ensure traceability in practice:
- Link each cost to the overall project activity
- Use internal project codes in accounting
- Include explanatory notes for costs that may raise questions
- Regularly check that accounting records and supporting documents match
- Organise clear folders by cost category
Example:
External consultancy: €500 invoice recorded with a project code and explanatory note → smooth audit.
Practical organisation
Keeping everything organised prevents stress and errors. A simple approach:
- Folders by cost category
- Original documents + accounting records
- Explanatory notes where something may not be obvious
To make things easier, we have prepared a downloadable checklist where you will find all cost categories, required documents, and practical notes to help you prepare your cost evidence without missing any details.
Because, in the end, when documentation is well-structured and traceability is clear, an audit stops being a concern and becomes simply a verification of a job well done.
One final tip: don’t leave document review until the end of the project. Keeping things organised continuously saves time, reduces risks, and makes any audit run much more smoothly.
At INNOVARUM, we support organisations like yours to ensure that the financial management of your European projects is clear, solid, and fully prepared for any audit process.
If you want to strengthen your cost organisation or prepare for an audit with peace of mind, we will be happy to assist you