If an accountant or a filing service prepared your return, there are a handful of figures worth checking against your own documents before you file. Tracepaper gives you those figures and the working behind each one; it does not yet have a screen that lines two returns up side by side.

Pay and tax against the P60

SA102 box 1 should equal your P60's total pay for the year in that employment, and box 2 should equal the tax deducted. A return prepared from an earlier payslip, or before a late correction, can miss a figure the P60 later confirmed.

Pension contributions: net against gross, for relief at source

A relief-at-source contribution is paid net of basic-rate tax, and the return needs the grossed-up figure — what was paid, plus the 20% the provider reclaims — not the amount that left the account. A return using the net figure understates the basic-rate band extension and the annual allowance used.

The cost used for each share disposal

A base cost taken from a US broker's cost-basis figure, rather than from the sterling amount already charged to Income Tax at vest, can be the wrong figure for UK Capital Gains Tax — see the allowable cost of ESPP shares and the broker guides for the rule and the HMRC reference behind it.

The number of disposals

SA108 box 23 counts every disposal, including a same-day sale of shares sold only to cover the tax due at vest (why that sale still counts). A return that only counted voluntary sales can understate this figure even where it gets the tax right, because the gain on a sell-to-cover sale is usually nil.

What this actually gives you today

The figures for each of the above, and the working behind each one — the document, the page and the rule it came from — to set beside a return someone else prepared. It does not compare the two returns for you.

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