Confused with "Underpaid tax this year included in tax code next year"

[wildraid]

Hello,

I am filling the online SA form for 2016-2017 tax year. It is my first time, so I am a bit confused with questions 7 and 8 on "Tax calculation summary" page.

The question is: Underpaid tax for 2016-2017 included in your tax code for 2017-2018 - enter the amount shown as "estimated underpayment for 2016-2017" from your P2, "PAYE Coding Notice".

But I have never received P2. I only have payslips and multiple letters from HMRC about changes in my tax code.

My tax code on the first month of 2017-2018 was K252.
My tax code at this moment is K1097X.
This is what I see on the HMRC online portal in tax code details right now: https://imgur.com/a/xj5Ix

Should I trust online portal and input 1974.31 in box 8?
Or should I try to obtain P2 somehow or ask my employer?

The whole system is really confusing. HMRC changes my tax code and estimations every couple of months. I am not sure it will be the same when HMRC officer picks my SA.

[wildraid]

I am sorry for grammar mistakes in the original posts. It seems that edit function is not available after posting.

Just one more little detail. If I don't put anything in boxes 7 and 8, my tax software automatically estimates underpayment of ~1890. It's a bit less than HMRC estimation on online portal. Is it possible that HMRC slightly overestimates underpayment in PAYE code?

Thanks!

[SteLacca]

But I have never received P2. I only have payslips and multiple letters from HMRC about changes in my tax code.

Double check those "letters". They would, typically, be the P2.

[bd6759]

Phone HMRC and ask them for the figures you should put in these boxes.

And make sure you address is correvct because you should get a notice of coding every time they chnage it.

[wildraid]

But I have never received P2. I only have payslips and multiple letters from HMRC about changes in my tax code.

Double check those "letters". They would, typically, be the P2.

Ah, yes, you're right! I've checked the latest letter, and it has a very small "P2" print in bottom-left corner. I was naturally looking for this code somewhere at the top of page. I've also managed to find the note titled "Tax you owe (earlier year)". It states 1947 GBP which corresponds with value in HMRC online portal.

Great, that's it! Problem solved.
What is really funny, those letters look a bit different. Wording and format is not the same, but values are OK.

Thank you so much!