You can change your employment allowance claim partway through the tax year if required. This allows you to reclaim your full entitlement for the rest of the tax year. 

Once you state that you're not eligible for employment allowance, you'll see the message below on the Summary screen:

 To change the claim

1. Select Summary from the menu bar.
2. Under HMRC Real Time Information (RTI) Scheme, select Actions and Record Payment / EPS.
   
   NOTE:

   If you don't have an Actions button it means you aren't ready to complete your next EPS. Return to these steps once you've completed the pay runs in this reporting period.

3. Change the Eligible for NI Employment Allowance dropdown menu to Yes or No as required.
   The selected option will remain on each future EPS you submit.  You can change this again if required.
4. Complete the rest of the EPS as normal.

The change gets submitted to HMRC, and the summary page updates to show if you aren’t eligible. 

Any allowance amount claimed earlier adds back onto your HMRC liability.

If you've claimed employment allowance on a previous payroll system this tax year, you need to enter your employment allowance values. 

I forgot to enter my Employment Allowance to date