The solidarity surcharge was for decades an additional deduction of 5.5% on your wage tax. The good news: since 2021, you most likely no longer pay it. For around 90% of all employees, it has been completely eliminated.
Are you affected? The surcharge now only applies if your annual wage tax exceeds €20,350 (single) or €40,700 (married). That corresponds to a taxable income from around €75,000 for singles. Specifically: with a monthly gross salary of €6,000 (€72,000 annually), as a single person you don't pay the surcharge yet. It only starts to kick in from around €7,700 gross per month – and even then only within the transition zone at a reduced rate.
Practical note: our gross-net calculator automatically calculates whether you pay the surcharge and how much. If you're close to the threshold, it can be worth reducing your income below the limit through work-related expenses or other deductions – that saves you the entire surcharge.