Every deadline your business needs to hit in September 2026 — explained simply, with what each filing involves and exactly what it costs to miss it.

September is the most compliance-intensive month of the financial year for Indian businesses. Three major obligations converge in a single 30-day window: GST return filings for August, the second installment of advance tax for FY 2026-27, and the monthly TDS deposit cycle. Most crucial is furnishing of Audit Report under section 44AB (of Income-tax Act, 1961 as applicable for FY 2025-2026) on or before due date i.e. 30th September 2026. A single day delay may cost a heavy penalty which may extend to 1.50 Lakh.

For businesses with turnover above ₹5 crore, GSTR-3B is due on 20 September. The advance tax second instalment — 45% of estimated annual liability, cumulative — is due on 15 September. The TDS deposit for August deductions is due on 7 September. If your business falls under all three, you have a significant cash flow obligation in a single fortnight.

This blog gives you every deadline for September 2026, explains what each involves, and gives you the penalty calculation for any you miss — so you can prioritize correctly and avoid paying a rupee more than you owe.

All September 2026 Compliance Deadlines at a Glance

This is your complete compliance calendar for September 2026. Dates shaded in blue are GST deadlines; those in green are income tax and TDS deadlines.

TDS Compliance in September 2026

TDS Deposit — 7 September 2026

Any TDS deducted from payments made in August 2026 must be deposited with the government by 7 September 2026. This applies to salary TDS (deducted monthly from employee salaries), TDS on contractor payments, professional fees, rent, interest, commission, and any other payment where TDS is applicable under the Income Tax Act, 2025.

Governing law: Since all August 2026 payments occur after 1 April 2026, TDS is now governed by Section 393 of the Income Tax Act, 2025 (not Sections 194C, 194J, 194H etc. of the old Act). When depositing TDS, ensure your challan quotes the correct new section reference. Portal validation may fail if old Act section numbers are used for post-March 2026 transactions.

Advance Tax: The 15 September Deadline Explained

The 15 September deadline is the second of four advance tax installments for FY 2026-27. It is also the most misunderstood — because the percentage required is cumulative, not just for the quarter.

What ‘cumulative 45%’ means in practice: If your estimated annual tax liability is ₹3 lakh, you must have paid a total of ₹1,35,000 by 15 September — including whatever you paid on 15 June. If you paid ₹30,000 in June (10% — below the required 15%), you need to pay at least ₹1,05,000 in September to reach the 45% cumulative threshold. The shortfall from June also attracts interest.

Who is exempt from advance tax:

• Senior citizens (above 60 years) with no business or professional income — fully exempt from advance tax
• Presumptive taxation taxpayers under Section 44AD and 44ADA (small businesses and professionals with turnover/receipts below the prescribed limits) — can pay 100% of advance tax as a single instalment by 15 March 2027
• Salaried individuals whose entire tax liability is covered by employer TDS — no advance tax required

GST Filing Deadlines in September 2026

GSTR-1: Outward Supply Return — 11 September 2026

Monthly GST filers must report all B2B and B2C invoices issued in August 2026 by 11 September. With GSTR-3B hard-locked since July 2025, GSTR-1 accuracy is more important than ever — errors cannot be corrected directly in GSTR-3B and must go through GSTR-1A before GSTR-3B is filed.

• Critical for September specifically: Any FY 2025-26 invoice that has not yet been reported or was reported with errors must be amended in September’s GSTR-1 (Table 9A). The November 2025 amendment cut-off has passed — September is the last practical window to capture FY 2025-26 output corrections before year-end.
• QRMP filers: September is the last month of Q2 (July–September). Your quarterly GSTR-1 for Q2 is not due until 13 October 2026. However, if you have B2B buyers whose ITC depends on seeing your August invoices in their September GSTR-2B, use the Invoice Furnishing Facility (IFF) before 13 September to upload those invoices for the month.

GSTR-3B: Summary Return + Tax Payment — 20 September 2026

GSTR-3B for August 2026 is due 20 September for monthly filers. This is simultaneously the most important deadline this month and the one with the most cash flow impact — particularly for businesses that also owe advance tax by 15 September.

• September-specific cash flow alert: If you owe both advance tax (15 Sep) and GSTR-3B tax payment (20 Sep), plan your liquidity carefully. Both are cash outflows within 5 days of each other. For a business with ₹50 lakh monthly GST turnover, the GSTR-3B net tax payment alone can be ₹3–8 lakh. Add the advance tax instalment and the combined cash requirement in one fortnight is material.

PMT-06: Monthly GST Payment for QRMP Taxpayers — 25 September 2026

QRMP taxpayers file GST returns quarterly but pay tax monthly. The August 2026 tax payment via Form PMT-06 is due by 25 September. The amount can be calculated using either the Fixed Sum Method (35% of previous quarter’s GSTR-3B tax) or the Self-Assessment Method (based on actual August ITC and liability). If August was a high-revenue month compared to last quarter, the Fixed Sum Method may underpay — use the Self-Assessment Method for accuracy.

Tax Audit Report Deadline — 30 September 2026

Businesses and professionals whose books are required to be audited under Section 44AB must have their Chartered Accountant sign and upload the tax audit report (Form 3CD/3CA/3CB) by 30 September 2026. The ITR filing deadline for audit cases is 31 October 2026 — which is directly dependent on the audit report being completed first.

Who this applies to:

Businesses with turnover above ₹1 crore (₹10 crore if cash transactions are below 5%), and professionals with gross receipts above ₹50 lakh (₹75 lakh under presumptive scheme). Directors of private limited companies and partners of auditable firms also need to ensure the entity-level audit is complete before their personal ITR deadline.

What Each Missed Deadline Costs You: September Edition

September’s deadlines are more expensive to miss than most months — because three of them carry compounding consequences.

Planning Your September Cash Flow: The Fortnight That Matters

For any SME owner juggling GST, TDS, and advance tax simultaneously, September requires deliberate cash flow planning. Here is the sequence of outflows and what to prepare:

September Has Three Deadlines in One Fortnight. Let’s Make Sure You Hit All of Them.

Related Reading

→ July 2026 GST & TDS Due Dates: Don’t Miss These Compliance Deadlines

→ Advance Tax September 15 Deadline: How to Calculate & Pay Correctly

→ Quarterly Review: How to Reconcile GST & Books Before Q2 Ends

→ 10 Signs Your Growing Business Needs a Virtual CFO Right Now

The post September 2026 GST, TDS & Advance Tax Calendar: What You Need to Know for Simple Filing first appeared on CPC Services Pvt. Ltd..

July is one of the most deadline-heavy months in the Indian compliance calendar. GST returns for June need to be filed. TDS deposited in June must be paid to the government. And for non-salary TDS deductors, Q1 of Tax Year 2026-27 closes on 31 July — meaning the quarterly TDS return is also due this month.

Missing even one of these deadlines does not just mean a penalty. It means interest charges that compound monthly, potential notices from the GST or Income Tax department, and — in the case of TDS non-deposit — the risk of expense dis-allowance in your books.

This guide gives you every key date for July 2026, explains what each filing involves, what happens if you miss it, and what to do if you are already behind.

All July 2026 Compliance Deadlines at a Glance

Check this table first. If three or more of these apply to your business, read the full explanations below.

GST Filing Deadlines — July 2026

GST compliance in July covers the June 2026 monthly cycle and, for QRMP taxpayers, the close of Q1 (April–June 2026). Here is what each filing involves.

GSTR-1: Outward Supply Return

GSTR-1 is where you report all your sales invoices for the month. Every registered supplier must file it — and it must be done before GSTR-3B, because your buyers’ input tax credit (ITC) depends on it appearing in their GSTR-2B.

Monthly filers (turnover > ₹1.5 Cr or opted for monthly): Due 11 July 2026

• QRMP quarterly filers (turnover ≤ ₹5 Cr): Due 13 July 2026 (for the full Apr–Jun 2026 quarter)

GSTR-3B: Summary Return + Tax Payment

GSTR-3B is the most important monthly GST filing. It is a self-declared summary where you report your total output tax, claim input tax credit, and pay the net GST amount. If there is no reconciliation between GSTR-1 and GSTR-3B, you risk notices and ITC mismatches for your buyers.

Monthly filers: Due 20 July 2026

• QRMP — Category 1 states: Due 22 July 2026
• QRMP — Category 2 states (Haryana, Delhi, UP, Punjab, Rajasthan, Bihar, WB, and others): Due 24 July 2026

GSTR-7 and GSTR-8: TDS & TCS Under GST

• GSTR-7 is filed by entities that deduct TDS under GST (government bodies, PSUs, and certain notified persons). Due: 10 July 2026.
• GSTR-8 is filed by e-commerce operators who collect TCS on behalf of sellers on their platform. Due: 10 July 2026.

TDS Compliance Deadlines — July 2026

Tax Deducted at Source (TDS) has two distinct obligations: the monthly deposit of tax already deducted, and the quarterly return filing that reports all deductions made during the quarter. July 2026 is particularly important because the Q1 TDS return deadline falls on 31 July.

TDS Deposit — 7 July 2026

Any TDS deducted from payments made in June 2026 — whether salary, contractor fees, rent, professional charges, or interest — must be deposited with the government by 7 July 2026.

• Who this applies to: Any business or individual/HUF whose turnover exceeded ₹1 crore (business) or ₹50 lakh (professional receipts) in the previous year, and who made TDS-applicable payments in June.
• Important note from April 2026: TDS from 1 April 2026 onwards is governed by the Income Tax Act, 2025 — not the old Act. Section references on challans for post-March payments must use the new numbering under Section 393. If your payroll or accounting software has not been updated to reflect the new Act, your TDS returns may have incorrect section references — which can trigger validation errors.

Q1 TDS Return — 31 July 2026

The quarterly TDS return covers all deductions made between April and June 2026 (Q1 of Tax Year 2026-27). It must be filed even if TDS deposits were made on time every month — the return is a separate obligation from the monthly deposit.

Key forms: 

• Form 24Q — Salary TDS (employer deducting from employee salaries)
• Form 26Q — Non-salary TDS to residents (contractors, professionals, rent, etc.)
• Form 27Q — TDS on payments to non-residents and foreign companies
• Form 27EQ — TCS (Tax Collected at Source) on various items

Deadline: 31 July 2026

TDS on Property Purchase — 30 July 2026

If your business or any individual purchased immovable property in June 2026, TDS on that transaction must be deposited by 30 July 2026. This applies to property purchases above ₹50 lakh. The challan-cum-statement is filed as Form 26QB and must be submitted within 30 days of the end of the month in which the purchase was made.

What Happens If You Miss These Deadlines

Most SME owners understand that missing deadlines causes penalties. What many do not realize is how quickly those penalties compound — and the less obvious consequences that follow.

Already Behind? What to Do Right Now

If you have missed a GST or TDS deadline in June or earlier, the priority is simple: file now, pay the applicable late fee and interest, and put a system in place so it does not happen again. The longer you wait, the higher the penalties — and the greater the chance of a formal notice.

For GST late filing: 

• File the pending GSTR-1 or GSTR-3B immediately on the GST portal. Calculate and pay the late fee (₹50/day, capped at ₹5,000 for GSTR-3B) and 18% interest on any unpaid tax. A reconciliation should be done to ensure the pending return does not create an ITC mismatch for your buyers.

For TDS late deposit: 

• Deposit the TDS amount immediately with the applicable interest at 1.5% per month. Then file the quarterly return (Form 24Q / 26Q / 27Q) before the deadline or as soon as possible. Note: interest must be paid before the return is filed — the portal will not allow filing with outstanding interest.

For TDS return late filing: 

• Pay the ₹200/day fee (capped at the TDS amount for the quarter) and file immediately. A penalty of ₹10,000–₹1 lakh under Section 271H applies for late filing, but this can be waived if you file within one year of the due date and pay all dues.

How to Never Miss a Compliance Deadline Again

The businesses that never face penalty notices are not the ones with the largest finance teams. They are the ones with the simplest, most consistent compliance systems. Here is what works:

1. Build a monthly compliance calendar. 

Map every GST and TDS deadline relevant to your business into a shared calendar with reminders set 7 days and 2 days before each due date. July’s deadlines — 7th, 10th, 11th, 13th, 20th, 22nd/24th, 25th, 31st — are not random. They follow a predictable pattern every month. Once the calendar is set up, it runs itself.

2. Reconcile before you file, not after. 

Every GSTR-3B should be reconciled with GSTR-1 before submission. Every TDS return should be verified against payment challans. Reconciliation is not extra work — it is the work that prevents six months of notice-handling later.

3. Separate the person who deducts TDS from the person who deposits it. 

In most SMEs, TDS defaults happen because the same person responsible for making payments is also responsible for depositing TDS — and the deposit gets deprioritised when cash is tight. A simple approval workflow, or a professional partner handling TDS, solves this completely.

CPC Services acts as a compliance backbone for growing SMEs across Faridabad and Delhi NCR — managing GST filings, TDS deposits and returns, payroll compliance, and ROC deadlines as a single integrated service. Since 1987, we have ensured that our clients do not receive compliance notices. The ones who come to us after receiving a notice pay far more than those who came to us before.

→ Explore Accounting & Virtual CFO Services

→ Explore Corporate Compliance Services

→ Explore Payroll & HR Compliance

How is CPC Services different from a regular tax accountant for compliance?

A regular accountant files what is due. CPC Services builds and manages your entire compliance calendar — GST, TDS, ROC, payroll, advance tax — as a single integrated system. We reconcile before filing, flag issues before they become notices, and act as a Virtual CFO partner for businesses that have outgrown basic compliance. We have been doing this since 1987, across manufacturing, healthcare, retail, and professional services.

→ Explore Accounting & Virtual CFO Services

Related Reading

→ 10 Signs Your Growing Business Needs a Virtual CFO Right Now

→ Startup Budgeting 2026: How Founders Can Plan Smart for Growth

→ The Simple SME Accounting Checklist for a Better 2026

CPC Services manages GST, TDS, payroll, and corporate compliance for SMEs across Faridabad and Delhi NCR — so you never miss a deadline or pay an avoidable penalty.

🔗  Compliance Desk     |     📋  GST Services     |     💬  Talk to an Expert

The post The Most Important July 2026 GST & TDS Due Dates first appeared on CPC Services Pvt. Ltd..

Key Due Dates Businesses Must Remember

For every Indian business, GST compliance is non-negotiable. Missing a deadline doesn’t just mean a late fee — it can block Input Tax Credit (ITC) for your customers, disrupt cash flow, and even invite compliance notices.

According to GSTN data, over 1.4 crore taxpayers are registered under GST, and nearly 12–15% of returns are delayed every month — mostly due to last-minute filing or reconciliation errors.

October 2025 is a critical month. With the festive season driving sales and operations, many businesses tend to overlook filing schedules. This blog provides a complete GST calendar for October 2025, explains why these filings matter, and shares a compliance checklist to help you stay penalty-free.

GST Filing Deadlines in October 2025

Here’s your GST compliance calendar:

Pro Tip :
Mark these dates in your compliance calendar or use accounting software with GST reminders. Even a 1-day delay may cost ₹50/day (₹20 for nil returns) plus 18% annual interest.

Why These Deadlines Matter

• GSTR-1 & IFF → Critical for ITC claims of your customers. If you delay, your buyers cannot claim credit — which strains relationships.
  
• GSTR-3B → The backbone of GST compliance, summarizing sales, purchases, ITC, and liabilities. Any mismatch triggers notices under GST Section 61.
  
• GSTR-7 & GSTR-8 → Directly impact vendors and e-commerce sellers. Late filing blocks their ITC and causes reconciliation delays.

Did you know?
Over 25% of GST mismatches in India arise because vendors file GSTR-1 late. That’s why proactive reconciliation is crucial.

Compliance Checklist for October 2025

Stay penalty-free with this 5-step routine:

• Reconcile Books → Match GSTR-2B with purchase register before filing.
• Verify ITC → Claim only eligible credits (avoid blocked credits under Rule 36).
• Cross-Check Vendor Data → Ensure suppliers file GSTR-1/IFF timely.
• Plan Cash Flow → Keep GST liability funds ready by the 15th of the month.
• File Early → Avoid last-day portal glitches; traffic spikes on¹ 19th–20th.

Common Mistakes Businesses Make

• Filing GSTR-3B without ITC reconciliation → leads to mismatches.
• Ignoring IFF in QRMP → delays buyer’s ITC.
• Forgetting GSTR-7/8 → vendors lose temporary ITC access.
• Waiting till deadline → GST portal crashes cause failed filings.

Pro Tip:
Even filing a nil return on time builds a clean compliance record.

Impact of Missing October GST Deadlines

If you miss your filing schedule:

• Late Fee: ₹50/day (₹20 for nil returns).
• Interest: 18% per annum on unpaid taxes.
• Blocked ITC: Your customers cannot claim credit — impacting your credibility.
• Scrutiny Notices: Repeated delays may lead to GST audit or DRC-01 notices.

GST Compliance Made Simple

Managing multiple returns across states, vendors, and invoices can overwhelm SMEs and startups. That’s why many rely on professional GST consultants.

At CPC Services Pvt. Ltd., we help businesses with:

• Timely GST return filing (monthly & quarterly)
• ITC reconciliation and vendor compliance tracking
• Automated compliance calendars
• Advisory on tax planning, audits, and notices

Need expert GST support this October?

Contact us today for a free consultation.

October 2025 brings a packed GST calendar — GSTR-1, 3B, 7, 8, and IFF all due within weeks. For businesses, timely filing isn’t just a legal mandate — it’s an investment in credibility, cash flow, and growth.

About CPC Services Pvt. Ltd.

CPC Services Pvt. Ltd. is a trusted financial and tax consultancy firm based in Faridabad, Haryana, serving businesses, e-commerce sellers, startups, and professionals across India. With decades of experience, our team of Chartered Accountants, GST experts, and financial advisors provides end-to-end solutions in GST compliance, return filing, ITC reconciliation, tax planning, and business advisory.

We help organizations stay compliant, avoid penalties, and streamline tax operations, ensuring smooth cash flow and credible business practices.

You can reach us via email at 📧 info@cpcservices.co.in or by phone at 📞 +91-9910278975. 

Optimize Your GST Compliance Today:

Whether it’s GSTR-1, GSTR-3B, GSTR-7, GSTR-8, or IFF filings for October 2025, our experts ensure timely and accurate submission, so your business stays penalty-free and ITC claims remain intact.

The post All You Need to Know: GST Filing & Important Deadlines – Oct 2025 first appeared on CPC Services Pvt. Ltd..