Do I have to pay zakat, if I spend more than I earned in a year but have some savings (on which I already paid zakat)?
Zakat is paid yearly on surplus wealth, i.e. wealth you have accumulated and you own for more then one year since it has reached the zakat sum. If you owe this zakat-able sum every year, you still have to pay zakat on it.
It does not matter how much you earned and spent during the year, you only pay zakat on the total sum you own at the moment of paying zakat.
Zakat is paid on lunar year, preferably during Ramadan, which is what the sahabah used to do.
There is no Zakat on income except if you saved money out of that income and meet the 2 following conditions:
1- You saved that money for more than year.
2- You are more than the limit for Zakat which is 85 grams of pure gold (24K). You could check the gold prices online and calculate the limit.
Please note that you will have to pay Zakat if your savings is more than the limit even if you spent more than what you have earned this year. If you already paid that Zakat, then you should be good.
Please refer to the reference for more details.