1.1. Once a year only
Claiming Employment Allowance should only be done once a year. If you have already claimed for the current tax year, do not do it again.

1.2. How much can you claim?
An eligible employer is entitled to claim up to £5,000 in this current tax year (2023 - 24). Employment Allowance will reduce your employers’ (secondary) Class 1 National Insurance liability each time you run your payroll until the £5,000 is used up, or the tax year ends, whichever is sooner.

Eg:.Your total Employer Class 1 National Insurance liability for the year is £2000.00 the Employment allowance lowers your Employer Class 1 National Insurance each time you run payroll in contrast to your total liability.

1.3. When to claim for Employer Allowance?
You can claim Employment Allowance at any time during the tax year.

If you are continuing a claim from the tax year 2021/2023 to the tax year 2022/2024, you must send an EPS in month 1.

1.4. Can the unused Employment Allowance be carried forward?
The earlier you make an Employment Allowance Claim, the sooner you will get it. If you make a late claim and have a large unused Allowance, you will need to ask HMRC to do one of the following: offset the unused balance against other current or future PAYE liabilities so, wherever possible, the unused balance of the Allowance does not go waste, or give you a refund of any unused balance of the Allowance provided you do not have any other liabilities.

For more detailed information, please refer to the HMRC link

1.5. Can the Employment Allowance for earlier tax years be claimed?
Yes, you can make a claim for the Employment Allowance up to 4 years after the end of the tax year in which the Allowance applies. For example, if you want to claim Employment Allowance for the tax year 2018-2019, you must make your claim no later than 5 April 2024.

For more detailed information, please refer to the HMRC link