In the UK, you can put up to £40k /year into a private pension tax free. If you are a higher rate tax payer, you get a cash refund.

Whilst it wouldn't give you a higher current net income, it would be beneficial in the long run. There might be similar schemes in Austria.

If you are PAYE through your employer, there is little you can do really. If you can contract under a legal entity, that nunber might go up, but in the UK, you'd have to earn £100k+ for it to be worthwhile imo.

For context, I am a UK accountant.