Is the public calculator using the same rates as the SLTax360 platform?

Yes. The calculator reads from the same versioned state_tax_config_history table the production filing engine uses. There is no separate "free version" rate set.

Can the calculator handle retroactive filings or historical reconciliation?

Yes. Pass an effective_date and the calculator picks the rate version that was active on that day. This is how the platform itself handles endorsements, cancellations, and retroactive submissions.

Does the calculator file my transaction with the state?

No. The calculator only computes the tax breakdown. Filing — submission to OPTins, SLIP+, or the state portal — happens inside the SLTax360 platform.

How are fees taxed differently by state?

Each state configures which fee categories (policy fees, inspection fees, broker fees) are part of the taxable base. The calculator reads that configuration per state and folds eligible fees into the tax base before computing percentages.

Surplus Lines Tax Calculator — How It Works

Q: What is the rate limit on the public calculator?

Fifteen calculations per hour per IP. For programmatic use beyond that, the same engine is available as a REST API at $0.19 per call with no monthly minimum, or included free in the Enterprise plan.

The public SLTax360 tax calculator answers one question: given a state, a premium amount, and an effective date, what surplus lines taxes and fees apply? It returns an itemized breakdown — surplus lines tax, stamping fee, fire marshal, FIGA, regulatory surcharges, municipal taxes, flat filing fees — for any of the 50 U.S. states or DC. No signup, no API key. This article walks through what the calculator actually does so you can use it confidently for quoting, reconciliation, and double-checking filings.

Where the rates come from

Every rate, fee, and special-case rule the calculator displays is read from the same versioned configuration table SLTax360 itself uses to file your transactions in production. When a state legislature updates a rate, the new value is added with an effective_from date — the old value is preserved in history, not overwritten. That means the calculator can answer "what was the Texas rate on June 12, 2024?" as accurately as it answers "what is it today?"

This matters operationally. If you're reconciling an old filing or pricing a retroactive endorsement, you do not want a calculator that only knows today's rates. The same versioning runs underneath every state on the platform — try it on Texas, California, or Florida and you'll see the effective from date on each rate snapshot.

The math, in plain English

Surplus lines tax is almost never a single percentage of premium. Most states have layered components, and the order in which those components compute matters. Here is what the calculator does, in sequence:

Establish the tax base. For most states, the tax base is gross premium. Some states include policy fees in the tax base; others do not. The calculator checks the state's configured fee categories and adds eligible fees to the base before computing percentages.
Compute the surplus lines tax as a percentage of the tax base.
Compute the stamping fee, if the state has one, against the same base.
Apply any additional state-specific components: fire marshal tax, FIGA assessment, service fee, state surcharge, regulatory fee, SLAS/clearinghouse fee, municipal tax. Each is a separate percentage applied to the tax base.
Add any flat fees — a few states charge a fixed filing fee per transaction independent of premium size.
Apply the state's rounding rule to each line item: standard 2-decimal rounding, whole-dollar rounding, or no rounding, depending on the jurisdiction.

The output is an array of line items — one row per component — plus the unrounded amount, the final amount, and a total. You see exactly which dollar went where, which is the part that matters during a state audit.

Tax base and fee handling

The trickiest part of surplus lines math is not the percentages — it is the tax base. Whether a state taxes policy fees, inspection fees, or broker fees varies, and getting it wrong by even one component can push a filing into non-compliance.

The calculator supports two modes for fees. In the simple form, you pass a single policy fees number; the calculator checks whether the state's configuration includes that fee category in the taxable base and acts accordingly. In the detailed form (used by the REST API and by the platform itself), you pass an array of typed fees and the calculator routes each one to the right category — only the categories the state actually taxes get added to the base.

For the public web calculator, the simple form is exposed. For programmatic callers who need finer control over taxable vs non-taxable fees, the REST API accepts the detailed fee array.

Effective dates

Pass effective_date and the calculator picks the rate version active on that day. Omit it and you get today's rate. This is critical for endorsements, cancellations, retroactive filings, and historical reconciliation — the math has to match what was law at the time the policy was bound, not what is law right now.

If a state has a scheduled future rate change (effective_from in the future), the calculator continues to use the current rate until that date arrives, then automatically picks up the new version. Nothing to redeploy on your side; the configuration drives the behavior.

Rate limiting and what's free

The public calculator is throttled at 15 calculations per hour per IP. That's deliberately set so the page works for shopping, quoting, and verification but is uneconomical for scraping. If you need to integrate calculations into your policy admin system, AMS, or quoting tool, the same engine is available as a REST API at $0.19 per call with no monthly minimum. Request API access if that's a fit.

Enterprise plan subscribers get the API included at no extra cost. The calculator endpoint and the platform's internal calculation engine are the same code — there is no "free version is slightly wrong" trap.

How to read the output

A calculation result looks like this:

State — the resolved state ID, code, and name.
Input — the premium, policy fees, and effective date that were used.
Tax base — the dollar amount each percentage was applied against. This is the single most useful number for an audit, because it shows whether fees were folded in.
Line items — an array, one row per component, each with name, code, rate (or flat amount), rounded amount, and unrounded amount.
Total taxes and fees — sum of all line items, rounded.
Total due — premium + policy fees + total taxes and fees.
Special notes — any state-specific text from the rate configuration (filing peculiarities, multi-state allocation rules, etc.).

Save the JSON. When a state audit comes, you have a row-level breakdown of every calculation that ever fed a filing.

What it does not do

The calculator does not file your transaction. It does not allocate multi-state risk by exposure. It does not retrieve a policy from a carrier system. Those are jobs for the full SLTax360 platform. The calculator's job is to answer the math question correctly, fast, and in a format you can verify.

Using it for verification

The most valuable workflow for the calculator, if you are already using another filing tool, is verification. Run the same premium and state through the public calculator, then check the line items against your filing tool's output. If they disagree by more than a rounding cent, one of the two is using a stale rate, the wrong tax base, or the wrong rounding rule — and figuring out which is the kind of thing that prevents an awkward conversation with a state regulator.

Try it now, browse filing details by state, or book a 20-minute demo to see how the same engine drives end-to-end filing for an MGA or wholesale brokerage.