Self Assessment / pension / tax calculating

jnorth55

If people are interested, after using this Taxgrid calculator I've also been able to work out why other online calculators aren't accurate. The ones on known websites tend to confuse the different types of pension (workplace, sipp etc), but perhaps more 'interesting' is that the AI based ones are really inaccurate because instead of them calculating that contributions extend the 20 or 40% tax band they instead sometimes assume they raise the level at which you start paying tax.

DRS1

Sounds like you should be talking to this chap

Follow-up: comparison of UK take-home calculators (pension + student loan handling) — MoneySavingExpert Forum

InspectahDave

https://forums.moneysavingexpert.com/discussion/comment/81909265#Comment_81909265

Thanks for bringing me in here!

This is actually something I ran into recently as well. I was trying to understand why different UK tax calculators were producing different results for the same inputs, particularly once pensions were involved.

To get a clearer picture I ended up comparing several of them side-by-side using a few standardised scenarios (simple PAYE, higher income with pension contributions, salary sacrifice etc.) and looking at how each one handled the calculation.

What became apparent quite quickly is that many tools simplify or label pension mechanisms differently — for example net pay vs relief at source vs salary sacrifice — and that distinction affects things like adjusted net income, tax band extension, NI and student loan calculations.

When those mechanisms aren’t clearly modeled or explained, two calculators can produce different answers even when the inputs appear identical.

Dazed_and_C0nfused

https://forums.moneysavingexpert.com/discussion/comment/81909258#Comment_81909258

The problem with this explanation though is that the type of pension isn't really relevant.

It's the method used to make the contributions which is key.

And this forum has consistently highlighted that an awful lot of people have no idea which method(s) applies to the contributions they make.

Or as is often the case, the contributions they don't in fact make.

jnorth55

https://forums.moneysavingexpert.com/discussion/comment/81909661#Comment_81909661

I'm not sure where your coming from with this comment. Some of the calculators I tried did indeed confuse the type of pension, for example assuming the contribution was a workplace one rather than a SIPP, which have different effects on tax, one (workplace) being irrelevant for self assessment calculations except when they are part of income.

Dazed_and_C0nfused

https://forums.moneysavingexpert.com/discussion/comment/81909718#Comment_81909718

I have no idea why you think that?

AIUI it would be possible for a SIPP to receive contributions made via a variety of methods.

And a "workplace" pension certainly can.

And the different methods work in a variety of different ways from a tax (and NI) perspective.

jnorth55

https://forums.moneysavingexpert.com/discussion/comment/81909773#Comment_81909773

I think your misunderstanding. I was talking about why some online calculators are inaccurate, as in how they have been inadequately designed. You seem to be talking about people using them not knowing what they're doing.

InspectahDave

https://forums.moneysavingexpert.com/discussion/comment/81905800#Comment_81905800

Yes, this is exactly what I found.

A lot of the online calculators support slightly different things (pension types, salary sacrifice, dividend treatment, student loans etc.), and when you start testing edge cases the results can vary quite a bit.

To probe deeper, I decided to do a comparison across a number of UK tax calculators using a few standard scenarios just to see how consistent they actually are.

I put the results in a spreadsheet here if it's useful:
https://docs.google.com/spreadsheets/d/1utdFvHbMP2UF-E8qfA7rRWl4K7tsX5K5qe0jZvKFpQY/edit?usp=sharing

It includes the scenarios I used and the outputs each calculator produced.

Happy to add more scenarios as well if there are particular cases people want to test (pension contributions around the higher rate boundary are especially interesting).

jnorth55

On another calculator point; has anyone found a reliable calculator or at least website that explains, clearly, the various fees charged from the different pension providers? What I mean specifically is, for example, sites such as Nest & Pensionbee have one fee as a %, whereas Aviva, Vanguard etc, have a management fee which is usually lower that those others but then additional fees for various aspects of how they run the funds. I know there are more variations with the 'self build' options with Aviva, Vanguard etc. but I'm sure there must be a website somewhere which tries to work out what the real % is when compared to those that have a single fee.

jnorth55

https://forums.moneysavingexpert.com/discussion/comment/81906256#Comment_81906256

Well, it seems Taxgrid's website is down!