📊 Q3 Tax Closing: Keys to Preparing Your Tax Returns

Next Wednesday, 30 September, is the tax closing of the third quarter of the 2026 tax year (Q3). For any SME, startup or self-employed worker, the last week of September is a critical window of opportunity. It is not just about closing the calendar month, but about reviewing the accounts in advance to plan carefully the tax returns that must be filed with the Spanish Tax Agency between 1 and 20 October.

Reactive tax management —gathering receipts and invoices in a rush in mid-October— creates unnecessary cash-flow pressure, leads to the loss of perfectly legitimate deductions and multiplies the risk of formal inconsistencies that end in requests or penalty proceedings. At Ruiz & Asociados we apply a principle of technical prevention: reviewing the financial position before 30 September is the only way to guarantee compliance and optimise your company’s tax bill.

📑 Technical breakdown of the October tax obligations

Between 1 and 20 October, individuals and companies carrying out economic activities in Spain must file and pay a series of official forms for the period from 1 July to 30 September.

       OCTOBER 2026 TAX CALENDAR
  ┌──────────────────────────────────────────────┐
  │ 1 - 15 October: direct debit                 │
  │ 1 - 20 October: filing and payment           │
  └──────────────────────────────────────────────┘
                         │
      ┌──────────────────┼──────────────────┐
      ▼                  ▼                  ▼
       VAT          IRPF WITHHOLDINGS   PAYMENTS ON ACCOUNT
    Form 303         Forms 111/115      Forms 130/131/202

1. Value Added Tax (Form 303)

Form 303 calculates the difference between the VAT charged to customers on invoices issued and the deductible VAT paid on business expenses.

• Accrual rule: VAT accrues on the date the invoice is issued or the service is provided, regardless of whether the customer has paid (unless the company uses the special cash accounting scheme).
• VAT pro rata: companies that carry out both transactions with a right to deduct (e.g. product sales) and exempt transactions (e.g. regulated training or healthcare services) must apply the pro rata rule to determine what percentage of input VAT they can deduct.

2. Personal income tax payments on account (Forms 130 and 131)

Self-employed workers under the direct assessment regime (Form 130) must pay 20% of the net income earned from 1 January to 30 September, minus the payments on account and tax withheld in previous quarters. Those under the objective assessment (module) regime file the cumulative Form 131.

3. Withholdings and payments on account (Forms 111 and 115)

• Form 111: return and payment of the tax withheld on employees’ payslips, directors’ pay and invoices from independent professionals during the quarter.
• Form 115: payment of the 19% withholding on rent for urban premises where the company carries out its business, unless the landlord provides an exemption certificate issued by the AEAT.

4. Corporate Tax payment on account (Form 202)

In October, companies must make the second Corporate Tax payment on account for 2026. Depending on their volume of operations (and whether they use the previous year’s tax liability —Art. 40.2 LIS— or the taxable base for the first 9 months —Art. 40.3 LIS—), the advance amount is calculated on the cumulative tax result.

🛠 5-step checklist to complete before 30 September

To reach the filing period with consolidated accounts, we recommend this accounting review protocol:

1. Request and close supplier invoices: ask your suppliers for all receipts for expenses incurred in July, August and September. An expense without a full invoice (or recorded only with a till receipt) will not allow you to deduct the input VAT in the October Form 303.
2. Check expense deductibility: filter the accounts to isolate doubtful expenses. For an expense to be accepted, it must be linked to income, properly recorded and supported by documents. Exclude personal purchases or those unrelated to the business to avoid issues in a possible tax inspection.
3. Record depreciation and investment assets: check whether you have acquired investment assets this year. Correctly applying the tax depreciation tables (or free depreciation for SMEs in certain cases) reduces the quarter’s net tax burden.
4. Bank reconciliation and cash traceability: match the company’s bank statements with the accounting journal. Approved accounting technology tools make it faster to find mismatches between receipts, payments and indirect taxes.
5. Cash forecast for 20 October: calculate the total amount of the returns in advance to make sure the bank account has enough funds. Remember that the deadline for paying taxes by direct debit ends on 15 October.

🔍 Assessing your marginal rate: is it time to set up a company?

The Q3 closing is the ideal moment to review the legal structure of the business. If you operate as a self-employed individual and your cumulative net income at this point in the year puts your marginal income tax rate above 25% (the general Corporate Tax rate), personal taxes may be draining the business’s ability to reinvest.

In growing projects or those following self-financed models such as bootstrapping in 2026, analysing whether it makes sense to move from self-employed to a company before the year-end closing helps optimise taxes and protect the founder’s personal assets.

🛡 Voluntary correction: the right to make mistakes

If, while consolidating Q3 data, you find that you made mistakes in your first or second quarter returns (Q1 or Q2) —such as omitting income, an error in the VAT pro rata or a duplicated deduction—, tax law provides ways to correct them.

Under the right to make mistakes, voluntarily filing a supplementary or corrective return before receiving any notification or request from the AEAT allows you to regularise the tax debt without administrative penalties, applying only the late-filing surcharges set by law.

You can check the tax calendar deadlines and applicable rules directly in the e-office of the Spanish Tax Agency or in the Official State Gazette.

🏢 Ruiz & Asociados: comprehensive tax and accounting planning

At Ruiz & Asociados we have spent more than 30 years providing high-level tax, accounting and corporate management to SMEs, startups and independent professionals. 🤝

Our team of economists and tax advisers continuously reviews our clients’ accounts, ensuring strict compliance with tax law, maximising the deductions available and preventing administrative deadlines from compromising your cash flow.

Do you want to close the third quarter knowing your taxes are fully optimised? At Ruiz & Asociados we take technical charge of your accounts. Contact our firm today and let us design your strategy for the October returns. 🚀