Dietas are an autónomo's meal expenses during work related travel, deductible only under strict conditions: eating at a restaurant or hospitality establishment, paying electronically (never in cash), and being able to show the link to your business activity. The daily cap without an overnight stay is 26.67 € in Spain and 48.08 € abroad, the same limits that apply to employees' tax free per diems.
The tax agency scrutinizes this deduction closely: weekend meals, meals near your home, or anything paid in cash tend to be rejected. Keep the invoice or receipt plus the proof of electronic payment for every meal you deduct.
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