VAT mistakes are costly. Errors on your return can result in penalties, interest charges, and unwelcome attention from HMRC. Many businesses make the same VAT errors repeatedly—often without realizing they're getting it wrong. This guide covers the five most common VAT mistakes and how to avoid them.
1. Incorrectly Claiming VAT on Exempt Supplies
One of the most frequent VAT errors is claiming input tax (VAT you've paid) on supplies that are exempt or outside the scope of VAT. This includes financial services, insurance, membership fees to non-trading organizations, and certain medical treatments.
Why it matters: If you claim VAT on exempt supplies, you're overclaiming your input tax, which reduces your VAT liability and triggers HMRC scrutiny.
How to avoid it: Keep detailed records of all expenses and their classification. When in doubt about whether a supply is VATable, consult HMRC guidance or ask your accountant. Use accounting software that helps categorize transactions correctly.
2. Missing the VAT Return Deadline
VAT returns must be filed by the same date you pay any VAT due. For most businesses, this is one month plus seven calendar days after the end of the quarter. Missing this deadline triggers penalties.
Why it matters: A single late return results in a £200 penalty (or 5% of VAT due, whichever is higher). Repeat offences compound the penalties and can trigger further interest charges and assessments.
How to avoid it: Mark VAT deadlines in your calendar with reminders 2-3 weeks in advance. If you struggle to meet deadlines, consider using software that flags due dates or hiring a bookkeeper to handle submissions. Filing online by HMRC's portal is now mandatory and the deadline is strict.
3. Miscalculating the VAT on Round Sum Invoices
Some businesses incorrectly calculate VAT on round sum invoices, particularly when they invoice in round figures like £100. If an invoice says "£100 including VAT" at 20%, the VAT is actually £16.67, not £20. Small rounding errors multiply across hundreds of invoices.
Why it matters: These errors accumulate. Over a year, miscalculating VAT on round sum invoices can mean you're overstating or understating your VAT return by hundreds of pounds—enough to trigger a correction or investigation.
How to avoid it: Use accounting software that automatically calculates VAT correctly. If invoicing manually, double-check the calculation: to find VAT on an amount including VAT, divide by 1.20 (or 1.05 for reduced rate), then subtract the original amount.
4. Not Keeping Proper Supporting Documentation
HMRC requires you to keep invoices, receipts, and records for at least 6 years. Many businesses keep digital copies but lose track of originals, or don't keep supporting docs for all claims. Without documentation, you can't prove your VAT claims to HMRC.
Why it matters: If HMRC audits your return and you can't produce receipts for claimed expenses, they can deny those claims. This means VAT becomes payable on revenue you thought was properly accounted for, plus penalties.
How to avoid it: Implement a document management system. Scan receipts and invoices monthly. Store them digitally with clear naming and organization. Use accounting software that links invoices and receipts to transactions. Organize by month and supplier.
5. Not Adjusting VAT Records When Credit Notes Are Issued
When you issue a credit note to a customer, the VAT on that credit note must be accounted for in your VAT return—not just the invoice amounts. The same applies to credit notes received from suppliers. Many businesses miss this adjustment.
Why it matters: Forgetting to include credit notes means your VAT return doesn't reflect the true VAT position. You're either overstating VAT due (meaning you pay unnecessarily) or understating it (meaning you face a correction and penalties).
How to avoid it: Ensure your accounting system automatically tracks credit notes as deductions from the related invoices. Flag credit notes during VAT reconciliation. Reconcile VAT monthly to catch these errors early before the quarterly return is filed.
Bonus Mistake: Not Reconciling VAT Records Regularly
Many businesses wait until the VAT return is due to reconcile their records. By then, mistakes have accumulated over three months and are harder to trace.
Best practice: Reconcile your VAT records monthly. This means matching sales invoices to sales list, purchase invoices to purchases list, and checking the VAT totals. Catching discrepancies early is far easier than sorting out a messy quarter-end reconciliation.
Your VAT Safety Checklist
Before submitting each VAT return, verify:
- •All invoices issued have been recorded with correct VAT amounts
- •All purchase invoices and receipts have been recorded and VAT is only claimed where VATable
- •All credit notes issued and received are properly accounted for
- •VAT totals on the return match your accounting records
- •Supporting documentation is stored and accessible
- •The return is being filed before the deadline
Takeaway
VAT compliance isn't complicated, but mistakes are common and costly. Most errors stem from poor record-keeping, lack of reconciliation, and not understanding VAT rules. By implementing regular reconciliation, using good accounting software, and keeping meticulous records, you can avoid these pitfalls.
If VAT is a headache for your business, we can help. Our team handles VAT returns for dozens of businesses, catching issues before they become problems. We ensure your records are accurate, your returns are filed on time, and you're never at risk of penalties.