Claim €0.23 per kilometer for all business travel. This rate increased from €0.21 and covers fuel, maintenance, depreciation.
With low turnover, you can opt for the KOR scheme and NOT charge VAT to clients. Simpler administration!
To deduct a portion of rent/mortgage as business expense, your home office needs a SEPARATE ENTRANCE and be used primarily for business.
If your partner helps in your business unpaid, you can deduct 1.25-4% of profit based on their hours.
With high profit, a BV structure might save taxes. BV profits are taxed at 19% (up to €200k) vs your marginal rate of ~49.5%.
Working 1,225+ hours/year as self-employed entitles you to the €2,470 zelfstandigenaftrek.
Working as ZZP but actually an employee (schijnzelfstandigheid) carries serious tax and legal risks for both you and your client.