Do I pay zakat on my monthly salary?

Not on each paycheck as it arrives, according to most scholars. Zakat is due on the part of your salary you have saved, once your savings reach the nisab and a lunar year has passed. Money you spend on rent, food and bills during the year is not zakatable.

Zakat is on savings, not income

This is the biggest difference from income tax. Zakat is a yearly duty on wealth you hold, and the Prophet ﷺ linked it to wealth that stays with you for a full year (Sunan Abi Dawud 1573). Your salary is a flow: it comes in, and much of it goes out again. What matters is what is left in your accounts on your zakat date.

وَأَقِيمُوا۟ ٱلصَّلَوٰةَ وَءَاتُوا۟ ٱلزَّكَوٰةَ "And establish prayer and give zakah..." Quran 2:43

How it works with a salary

Pick a zakat date. Many people choose a date in Ramadan, or the anniversary of the day their savings first reached the nisab.
On that date, total your savings: current account, savings account, cash, gold, investments.
Pay 2.5% of the total if it is above the nisab.

You don't need to track when each payslip arrived. Following the Hanafi approach, many scholars let you count all your savings on one date, even money that came in last month. It is the simplest and most common practice. See When do I have to pay zakat?

A minority view: zakat on receipt

Some contemporary scholars suggested that high earners pay 2.5% of their salary when they receive it, comparing it to the zakat on crops paid at harvest. Most scholars do not require this, but nothing stops you from setting aside 2.5% each month as advance zakat or as voluntary charity. See Can I pay zakat monthly?

What about pension deductions and taxes?

Income tax and national insurance deducted before you are paid were never in your hands, so they are not counted. Pension contributions have their own discussion. The money in your current and savings accounts is what you check. See Do I pay zakat on my savings account?

If you live paycheck to paycheck

If your balance never stays above the nisab, you don't owe zakat. That's not a failure. You can still give small sadaqah when you can, and you may even be eligible to receive zakat yourself.

Key points

No zakat is due on each paycheck by itself (majority view).
Zakat is 2.5% of what you've saved on your yearly zakat date.
Money spent during the year is not counted.
Setting aside 2.5% monthly is optional but can make it easier.

Tip: Set a recurring reminder for your zakat date and open a small "zakat pot" in your banking app. Moving a bit there each payday means the yearly payment never feels heavy.