A key requirement of maintaining your Spanish Non Lucrative Residence is the need to spend a minimum of 183 per year in Spain. At that point you will become tax resident in Spain, and you will be expected to pay taxes on your worldwide income.
You will also have to pay taxes in Spain if you have economic interests in the country, e.g. if you are self-employed or running a business in Spain. In addition, you may also be considered tax resident if your spouse and or children live in Spain.
Bear in mind that Spain has non-double taxation treaties in place with a host of countries, to prevent you from being taxed twice on the same income. You can view the list of countries here.
Should you invest in Spanish company shares, you’ll be eligible to pay capital gains tax to the Spanish revenue service. In addition, if you were to buy a property in Spain, this transaction may be subject to certain taxes as well.
It is always advisable to seek specialist tax advice about your unique financial situation before making any decisions about immigrating to Spain.