For exclusive pricing (tax added on top of the base), GST = Base × Rate ÷ 100, and Total = Base + GST. Substituting your numbers — Base ≈ ₹98,86,000, Rate = 6% — gives GST ≈ ₹5,93,160 and Total ≈ ₹1,04,79,160.

For inclusive pricing (tax already embedded in the sticker price), the calculation works backwards: Base = Total × 100 ÷ (100 + Rate), and GST = Total − Base. This matters because you cannot simply apply the rate directly to an inclusive total — doing so overstates the tax and understates the base, which is a common invoicing mistake.

• Taxable value (base): ₹98,86,000
• GST: ₹5,93,160
• Total: ₹1,04,79,160

India's GST system uses multiple slabs rather than a single flat rate, so the correct rate depends on how the specific good or service is classified under the notified rate schedule, not on the transaction amount. Broadly:

Slab classifications are notified and revised periodically by the GST Council, and specific items can move between slabs — treat this table as a general orientation, not a classification ruling, and check the current HSN/SAC-linked rate for your exact product or service before invoicing.

Every registered supply also carries an HSN code (for goods) or SAC code (for services), and it is that code — not the seller's own judgement of what "feels fair" — that ultimately determines the applicable slab. When in doubt on a new product line, look up the notified HSN classification or ask a GST practitioner rather than guessing based on a similar-looking item.

A registered business that pays GST on its purchases (inputs) can typically claim that amount as a credit against the GST it collects on its own sales (output), paying the government only the net difference. This mechanism is what makes GST a value-added tax rather than a tax that cascades at every stage of a supply chain.

ITC eligibility depends on conditions that this calculator does not evaluate — the supplier must have actually deposited the tax and filed their returns correctly, the recipient must hold a valid tax invoice, and certain categories of expense (like specified personal-consumption items) are blocked from ITC entirely regardless of documentation. Do not assume every GST amount you pay is automatically recoverable as credit.

In practice, most GST-registered businesses reconcile their purchase records against auto-populated data from suppliers' filed returns before claiming ITC, precisely because a mismatch (supplier didn't file, or filed a different figure) can lead to a credit being reversed later with interest — a good habit worth building even for a small business with only a handful of regular suppliers.

Seeing the same base amount move across different rates makes the arithmetic concrete. Holding a base of ₹98,86,000 constant:

• At 5%, GST is about ₹4,94,300, for a total of about ₹1,03,80,300 — typical of mass-consumption goods and essential services.
• At 18%, GST is about ₹17,79,480, for a total of about ₹1,16,65,480 — the most commonly applied standard rate.
• At 28%, GST is about ₹27,68,080, for a total of about ₹1,26,54,080 — the top slab, sometimes with an additional compensation cess layered on for specific luxury or “sin” goods.

The gap between the 5% and 28% totals on the same base — about ₹22,73,780 here — shows why correct classification matters far more than the base amount itself when it comes to how much tax actually changes hands.

Registered businesses typically file periodic returns declaring outward supplies (sales), inward supplies (purchases), and the resulting tax liability or ITC claim — the exact forms and frequency (monthly or quarterly) depend on your turnover and the scheme you are registered under. Filing late generally attracts a late fee and interest on any tax paid after the due date, even when the eventual liability is small.

This calculator does not prepare or file returns — it exists purely to get the base/tax/total arithmetic right for a single amount so you can invoice correctly and reconcile faster. Use dedicated GST return-filing software or your accountant for the actual filing workflow.

Small businesses below a specified annual turnover threshold can opt for the composition scheme, paying GST at a much lower flat rate on turnover instead of the standard slab rates, in exchange for simplified quarterly return filing. The trade-off: composition dealers generally cannot charge GST separately on invoices, cannot claim input tax credit, and cannot make inter-state outward supplies in most cases. This calculator models standard-scheme exclusive/inclusive pricing, not composition-scheme turnover tax — check current turnover thresholds and eligibility before assuming this scheme applies to your business.

Exclusive pricing adds GST on top of the base. Inclusive pricing embeds GST inside the sticker price — the calculator backs out base and tax differently. Your current results assume exclusive inputs based on the toggle above.

Before GST, India taxed goods and services through a patchwork of central and state levies — excise duty, service tax, VAT, central sales tax, octroi, and more — each with its own rate, return, and compliance process. A good moving across state lines could be taxed multiple times at different stages without full credit for tax already paid earlier in the chain, a problem commonly called “tax cascading” or a tax on tax.

GST replaced most of these with one indirect tax structure (split into central and state components for revenue-sharing purposes, though the end payer sees one combined rate), with input tax credit designed to flow through the supply chain and eliminate most cascading. This calculator’s base/GST/total split reflects that unified structure — one rate, one tax amount, rather than several layered levies.

• Retailers and shopkeepers quoting a final shelf price and needing to quickly confirm the tax-inclusive figure matches the intended margin.
• Freelancers and consultants above the registration threshold who need to add GST correctly to a service invoice.
• E-commerce sellers reconciling marketplace settlement reports where GST is shown separately from the listed price.
• Procurement and finance teams checking a vendor’s invoice for correct base/tax computation before approving payment.
• Students and exam candidates practising GST arithmetic for commerce, accountancy, or competitive exam syllabi.
• Small manufacturers pricing a finished good and wanting a quick before/after view of how tax changes the customer-facing price.

GST registration is generally mandatory once a business's aggregate turnover crosses a specified threshold in a financial year (thresholds differ for goods vs services and for special-category states), and is compulsory regardless of turnover for certain categories — including inter-state suppliers, e-commerce operators and sellers on e-commerce platforms, and businesses required to pay tax under reverse charge. Voluntary registration below the threshold is also allowed and can make sense if your customers need ITC on your invoices.

Once registered, a business must charge GST on taxable outward supplies, file returns on the applicable schedule, and maintain records that support both the tax collected and any credit claimed — obligations that continue even in periods with no sales, until the registration is formally cancelled.

A common real-world question is the mirror image of the standard calculation: “I paid ₹1,04,79,160 total — what was the base price and how much was GST?” This is exactly the inclusive-pricing math described above: Base = ₹1,04,79,160 × 100 ÷ (100 + 6) ≈ ₹98,86,000, and GST = ₹1,04,79,160 − ₹98,86,000 ≈ ₹5,93,160.

This reverse calculation matters most when you receive a bill showing only a final amount and need to back out the taxable value — for expense reporting, ITC claims, or simply verifying a vendor charged the correct rate. Toggle “inclusive” in the calculator above whenever you are starting from a known total rather than a known base.

A quick sanity check: multiplying the derived base by the rate and dividing by 100 should reproduce the same GST figure shown here, and adding that GST back to the base should reproduce your original total — if it does not, the rate you assumed is probably not the one actually applied on the bill.

• Applying the GST rate directly to an inclusive total instead of backing out the base first — this overstates both the tax shown and the amount remitted.
• Quoting a price to a customer without specifying whether it is inclusive or exclusive of GST, which causes disputes at billing time.
• Using the wrong slab rate because the product or service was misclassified under the HSN/SAC code.
• Forgetting to show the GST breakup (base, rate, tax amount) separately on the invoice, which most GST-compliant invoice formats require.
• Rounding each line item separately in a multi-item invoice instead of rounding only the final payable total, which can cause small reconciliation mismatches.

Discounts disclosed on the invoice itself (a trade discount shown as a line-item reduction) generally reduce the taxable value before GST is applied — so GST is charged on the discounted price, not the original list price. Discounts given after the invoice is issued (like a post-sale credit note) need specific documentation to reduce tax liability correctly. Free samples and gifts, in most cases, do not carry outward GST but can restrict the input tax credit the business claimed on the inputs used to make them — a nuance many small businesses miss.

Larger businesses above specified turnover thresholds are also required to generate e-invoices through the government's invoice registration portal, and e-way bills for the movement of goods above a specified value — both are compliance steps layered on top of the core base/tax/total arithmetic this calculator focuses on.

None of these additional compliance layers change the underlying base/GST/total relationship this calculator illustrates — they sit on top of it as procedural requirements once your business crosses the relevant thresholds.

• Assuming input tax credit is automatic just because GST was paid — it depends on the supplier's compliance and your documentation.
• Missing return filing deadlines, which can attract late fees and interest even if no tax is ultimately payable.
• Not reconciling your purchase records against your supplier's filed returns periodically, which is how many ITC mismatches are caught early.
• Treating this calculator's output as a filing-ready number — it is arithmetic on the amount and rate you provide, not a substitute for return preparation software or a tax professional's sign-off.
• Charging GST on discounted invoices at the pre-discount value instead of the post-discount taxable value where a trade discount is clearly disclosed on the invoice.
• Skipping e-invoicing or e-way bill requirements once your turnover or shipment value crosses the applicable threshold, assuming these obligations only apply to very large companies.

On balance, most tax professionals view GST as a meaningful simplification versus the pre-2017 patchwork, even though the multi-slab structure and periodic compliance calendar still require real ongoing attention from any registered business, however small.