Underpayment due to TWSS

Very confused about the underpayment due to TWSS that my employer can pay.

I was expecting that MyAccount would show the underpayment due to TWSS for my employment.
But all I can see is the overall preliminary result, which is a large underpayment.
In my situation they are not the same. Because part of the preliminary result underpaymnet is due to my spouse's TWSS.

I cannot expect that my employer will pay the whole of my preliminary result underpayment. Her employer is not going to contribute anything. Surely the system doesn't expect my employer to foot the bill.

Am I missing a separate calculation for each spouse of underpayment due to TWSS?

The system doesn't expect your employer to pay the bill. They can if they want but its not expected of them. Doubt many are. Its your tax bill. You both got TWSS and got paid tax free so now you have to pay tax.

Is there a way to see a breakdown of it, instead of the total?

Thanks for replying Sunny. I understand there is no requirement for the employer to pay, it is entirely a matter of goodwill. I was trying to express that I do not expect my employer to foot the bill for the underpayment due to my wife's TWSS and it seems the calculation at present implies so.

I'll try and explain better what I see the issue as. According to Revenue's guidance to employers (which I cannot link, apols, I'm not good on forums)
"You (the employer) must add additional 'IT Paid' and 'USC Paid' that equals the liability shown on the preliminary end of year statement. This must be done for each employer concerned"

by my reading of the advice to employers above, if the employer elects to meet the underpayment then they must pay the full amount of the preliminary result, which in my case includes my wife's underpayment. Partial payment is not possible - to quote: it must "Equal the liability shown on the prelim EoY statement".

To add to how wrong it is, the second sentance indicates that if they don't agree to pay the full underpayment for me, then they cannot pay the underpayment of any other staff member. Everyone gets the deal in full, or no-one, is my reading.

The above seems a ridiculous scenario to me. So I was thinking there must be a calculation of underpayment due to TWSS separate to the overall result in the preliminary result.

It's not just for married people like me that a problem presents with this scenario: for instance:
If I, like some people I know, had reduced the tax credits and tax bands applied to my job for the later half of the year to reduce my underpayment due to TWSS (as I was taxed on a week1 basis after coming off the TWSS), I would now be missing out on a tax free payment from my employer that my colleagues would be getting.

hope that clarifies my question.