Understanding Discrepancies in Tax Calculations Across HMRC, SA302, and Tax Software
When managing your taxes, you may notice differences in the amounts shown by HMRC, your SA302, and tax software like GoSimpleTax. These discrepancies can arise due to various factors, including Payments on Account, HMRC amendments, and differences in how refunds and liabilities are calculated. This article explains the common causes of these differences and provides guidance on reconciling them.
Common Causes of Discrepancies
1. Payments on Account
Payments on Account are advance payments toward your next tax year’s liability. If your tax liability exceeds £1,000, HMRC typically requires these payments, which are split into two installments due by 31 January and 31 July. These payments can cause discrepancies:
SA302 vs. GoSimpleTax: The SA302 shows your total tax liability for the year, while GoSimpleTax may subtract Payments on Account already made, showing a lower “amount due.” Both figures are correct but represent different stages of the calculation.
HMRC Submission Page: The HMRC submission page may show a higher amount due because it includes Payments on Account for the next tax year.
2. HMRC Amendments
HMRC may amend your tax return after submission for various reasons, such as:
Adjustments for underpayments included in your tax code from previous years.
Changes to pension details or student loan repayments.
These amendments can result in higher amounts due than initially calculated. To reconcile, review the amended tax calculation sent by HMRC, which typically includes a breakdown of the changes.
3. Refunds and Repayment Interest
If you are due a tax refund, the amount shown by HMRC may differ from what is calculated in GoSimpleTax due to repayment interest. HMRC includes repayment interest in the refund total, while GoSimpleTax only shows the calculated tax overpayment. Additionally, GoSimpleTax may assume that overpayments will be set against future Payments on Account, which can reduce the “amount due” displayed in the app.
4. Self-Employment Data on SA302
The SA302 only displays taxable self-employed profit. If your self-employment results in a loss, no taxable profit will appear on the SA302, and the calculation is correct. Ensure you have entered all income and expenses on the Self Employment (SA103) page to include them in the computation.
5. Processing Delays
After submitting your Self Assessment, HMRC can take up to 72 hours to process the return. During this time, your HMRC online account may show no amount due, even though GoSimpleTax indicates a payment is required. Ensure you make the payment by the statutory deadline regardless of the processing status.
Reconciling Differences
To reconcile discrepancies between HMRC, SA302, and tax software:
Check Payments on Account: Ensure all Payments on Account are recorded in your tax software. This will update the “amount due” to reflect these credits.
Review HMRC Amendments: Compare the HMRC calculation breakdown with your tax software’s figures to identify any adjustments. Common changes include pension entries or underpayments from previous years.
Understand Refund Calculations: Note that HMRC refunds may include repayment interest, which is not shown in GoSimpleTax. Adjust your expectations accordingly.
Verify Self-Employment Data: Ensure all self-employment income and expenses are entered on the correct pages in your tax software to reflect accurate taxable profit.
Account for Processing Delays: If HMRC shows no amount due immediately after submission, wait up to 72 hours for processing but ensure payment is made by the deadline.
FAQs
Does GoSimpleTax provide a full HMRC SA302 document?
GoSimpleTax generates an SA302-style summary and a full tax return PDF that mortgage lenders would accept . You can download the tax return and SA302 from the Reports page.
Why does the HMRC app show a higher amount due than my SA302?
This can occur if HMRC has added Payments on Account for the next tax year or amended your return. Review the HMRC calculation breakdown for details. By understanding these common causes and following the steps to reconcile differences, you can ensure your tax calculations are accurate and aligned across all platforms.