The short answer
After each quarterly update, HMRC works out a tax calculation from the figures it holds. SimpleTaxFlow shows it under Current, exactly as HMRC returns it. Estimate is our own figure and is labelled as an estimate. It does not estimate changes to dividends, pensions or savings interest. Quarterly updates are not payments. Tax is usually paid on 31 January and 31 July.
What HMRC’s calculation is
HMRC works out an in-year calculation from the updates and other information it holds for you. After HMRC accepts a change to your income, expenses or claims, SimpleTaxFlow asks HMRC for a new calculation. It shows HMRC’s figure, its date and the period it covers as HMRC returns them, including a negative figure.
The calculation is a point in time. It may change as HMRC receive more information during the tax year. It is not your final bill. Your bill is set when you submit your tax return.
How our estimate is different
Estimate is a SimpleTaxFlow figure, not HMRC’s calculation. When HMRC has a calculation, Estimate starts from HMRC’s figure as returned. It then adds our estimate of the tax on records you have not sent to HMRC yet. With no later records, it matches Current. Without an HMRC calculation, it uses your records only.
Our estimate covers self-employment and property income only. We do not estimate changes to dividends, pensions or savings interest, and the card says so. Changes to records inside a period HMRC already covers are not yet included. It uses rest of UK tax bands, without Scottish rates, student loans or personal allowance tapering. It is guidance only.
Quarterly updates are not payments
Sending an update does not pay tax or create a bill. You pay through Self Assessment. The usual dates are 31 January for the balancing payment and any first payment on account, and 31 July for any second payment on account.
For the 2026 to 2027 tax year, any first payment on account is usually due on 31 January 2027 and any second on 31 July 2027. The balancing payment is usually due on 31 January 2028. You do not usually make payments on account if your last Self Assessment bill was under £1,000, or if more than 80% of your tax was already taken at source. Check your HMRC online account for the amount and any different date.
Example (fictional)
A fictional sole trader sends the Q2 update in October 2026. Current shows HMRC’s calculation of £3,150, based on updates to 5 October 2026.
They then record £2,000 of income dated after 5 October in Bookkeeping. Estimate shows HMRC’s £3,150 plus our estimate of the tax on that £2,000. Nothing is paid when the update is sent.
1. Find the card
On Home the card is called Tax to set aside. In Tax it is called Income Tax to set aside. Choose Current for HMRC’s calculation, titled HMRC’s calculation: total Income Tax and NICs due. Choose Estimate for our figure, marked SimpleTaxFlow estimate with the date it was updated.
Open Tax2. Read the status
Pending means HMRC is still working it out. Not calculated means HMRC did not return a usable calculation. Not started means HMRC has no updates for this tax year yet. Reconnect means your HMRC connection has expired. Use the refresh icon, Refresh HMRC calculation, to request a new one. An unavailable figure does not mean you owe nothing.
Open Tax3. Open the full calculation
On Home choose View tax calculation. In Tax choose See HMRC’s calculation. Your tax position shows SimpleTaxFlow estimate beside HMRC tax to date. The HMRC calculation section lists the lines HMRC returned, such as Total income, Taxable income and Total tax & NICs due. Calculation history opens an earlier calculation. Your recorded income and Your recorded expenses list your records by category.
Open Tax4. Check your payment dates
In Tax, Payments lists the usual dates for the tax year. Each payment on account says If applicable. Choose Payments on account explained for HMRC’s rules. Check HMRC for the actual amount due and any different date.
Read about your MTD yearBefore you move on
- You know whether you are reading Current or Estimate
- HMRC’s calculation date and period match your latest update
- You read the note under Estimate about what it leaves out
- You checked HMRC for the amount you actually owe
- £30.00 + VAT a year or £3.50 + VAT a month. Bookkeeping is free. Pay when you send to HMRC.
Frequently asked questions
Why can HMRC’s figure be negative?
SimpleTaxFlow shows HMRC’s figure exactly as HMRC returns it, including a negative value. It is a point in time, not a repayment. Check your HMRC online account before relying on any refund.
Does the estimate include dividends or pensions?
Only where HMRC’s calculation already includes them. Our own estimate of later changes covers self-employment and property records only, and the card says so.
Why has HMRC’s calculation changed?
HMRC works out a new calculation as it receives more information, such as a new quarterly update or a change to your claims. Calculation history lists earlier calculations with their dates, so you can compare them.
Check the official rules
Tax rules can change and individual circumstances matter. Use HMRC’s current guidance to confirm the treatment that applies to you.
Put the guide into practice.
Open the relevant workspace and complete the next step with this guide available in another tab.
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