Excel Add-in

Calculate U.S. surplus lines taxes directly in Microsoft Excel with a single custom function. Use =SLTAX.SLAPI("Tax", "", "Texas", 10000) just like native Excel functions!

Key Features

Requirements

Installation

Option 1: Office Store (Pending Review)

1. Open Excel
2. Go to Insert → Add-ins → Get Add-ins
3. Search for "Surplus Lines Tax"
4. Click Add

Option 2: Sideload for Testing

1. Download the manifest.xml file from our GitHub repository
2. Open Excel
3. Go to Insert → Add-ins → My Add-ins
4. Click Upload My Add-in
5. Select the manifest.xml file
6. Click Upload

Configuration

Step 1: Get Your API Key

1. Go to app.surpluslinesapi.com
2. Sign in or create an account
3. Copy your API key from the dashboard

Step 2: Configure the Add-in

1. Click the Surplus Lines Tax button in the ribbon (Home tab)
2. Paste your API key in the Settings panel
3. Click Save API Key

Step 3: Start Using!

Type a formula in any cell:

=SLTAX.SLAPI("Tax", "", "Texas", 10000)

Result: 2×2 array spills with Base Tax (485) and Stamping Fee (18)

Function: SLTAX.SLAPI

Unified function for surplus lines tax calculations and rate lookups. Supports current and historical data with automatic fallback.

=SLTAX.SLAPI(calculationType, effectiveDate, stateCode, premiumAmount)

Parameters

Returns

For calculationType = "Tax": Returns 2-4 rows × 2 columns (Label | Value)

• Normal: Base Tax, Stamping Fee (2 rows)
• With Fallback: Base Tax, Stamping Fee, ⚠️ Notice, Rates From (4 rows)

For calculationType = "Rate": Returns 9-11 rows × 2 columns (Field | Value)

• Normal: 9 rows (tax_rate, stamping_fee, filing_fee, service_fee, surcharge, regulatory_fee, fire_marshal_tax, slas_clearinghouse_fee, flat_fee)
• With Fallback: 11 rows (adds ⚠️ Notice, Rates From)

Examples

=SLTAX.SLAPI("Tax", "", "Texas", 10000)

Returns 2×2 array:
| Base Tax      | 485 |
| Stamping Fee  | 18  |

=SLTAX.SLAPI("Rate", "", "Florida")

Returns 9×2 array:
| tax_rate                 | 4.94% |
| stamping_fee            | 0.05% |
| filing_fee              |       |
| service_fee             |       |
| surcharge               |       |
| regulatory_fee          |       |
| fire_marshal_tax        |       |
| slas_clearinghouse_fee  |       |
| flat_fee                |       |

=SLTAX.SLAPI("Tax", "2020-01-01", "Texas", 10000)

Returns 4×2 array (historical data unavailable, falls back to current):
| Base Tax      | 485                                           |
| Stamping Fee  | 18                                            |
| ⚠️ Notice     | No historical data available for 2020-01-01   |
| Rates From    | current                                       |

=SLTAX.SLAPI(A1, B1, C1, D1)

Where:
A1 = "Tax"
B1 = ""
C1 = "Texas"
D1 = 10000

Usage Examples

Basic Tax Calculation

Rate Lookup for Multiple States

=SLTAX.SLAPI("Rate", "", "California")

Returns 9×2 array with all fee fields for California

Historical Analysis

=SLTAX.SLAPI("Tax", "2024-06-15", "Iowa", 15000)

Calculates tax using rates from June 15, 2024 (or current if unavailable)

Batch Processing with Cell References

Test Template

Download our pre-configured Excel workbook with SLAPI function examples. The template includes 3 worksheets demonstrating current and historical queries.

What's Included

• Quick Reference — Function syntax, parameters, examples, and API key setup instructions
• Tax Calculator — Tax calculations for current and historical rates with automatic fallback demonstrations
• Rate Lookup — Single state rate lookups showing all 9 fee fields with examples for current and historical queries

Quick Start

1. Download the template above
2. Install the Surplus Lines Tax Add-in (see Installation)
3. Configure your API key
4. Open the template—formulas will calculate automatically!

Practical Examples

Simple Tax Calculation

Compare Rates Across States

// In cell C2: =SLTAX.SLAPI("Rate", "", A2)
// In cell C3: =SLTAX.SLAPI("Rate", "", A3)

Where A2 = "Texas" and A3 = "California"
Each formula returns 9×2 array with all fee fields

Audit Historical Policies

// Calculate tax using rates from policy effective date
=SLTAX.SLAPI("Tax", "2024-01-15", "Florida", 25000)

Returns current tax breakdown with fallback notice if 2024 data unavailable

Build a Multi-State Tax Table

// Create a table with states in column A, premiums in column B
// In C2: =SLTAX.SLAPI("Tax", "", A2, B2)
// Copy formula down for each state

Each formula automatically spills Base Tax and Stamping Fee

Troubleshooting

"API key not configured"

Open the Settings panel (click the Surplus Lines Tax button in the ribbon) and enter your API key.

Functions not appearing

1. Make sure the add-in is loaded (check Insert → Add-ins)
2. Try restarting Excel
3. Type =SLTAX.SLAPI and check if autocomplete appears
4. If you upgraded, Excel may be caching old functions - completely quit and restart Excel

"#SPILL!" error

The SLAPI function returns arrays that spill to adjacent cells. Ensure cells to the right and below the formula are empty:

• Tax calculations need 2 rows × 2 columns (or 4×2 with fallback)
• Rate lookups need 9 rows × 2 columns (or 11×2 with fallback)
• Clear any data in the spill range

"#VALUE!" error

Check that:

• calculationType is exactly "Tax" or "Rate" (case-insensitive)
• effectiveDate is in YYYY-MM-DD format or empty string "" for current
• State name is valid (use full names like "Texas" or 2-letter codes like "TX")
• Premium is a positive number (required for "Tax", optional for "Rate")
• You have API credits remaining

Old functions still showing

If you upgraded and still see old functions:

1. Completely quit Excel (not just close the workbook)
2. Clear Excel cache (Mac: ~/Library/Containers/com.microsoft.Excel/Data/Library/Caches/)
3. Restart Excel and reload the add-in

FAQ

Does it work on Mac?

Yes! The add-in works on Excel for Mac, Windows, and Web.

Do I need a Microsoft 365 subscription?

The add-in works with Excel 2016 or later, including standalone versions. Microsoft 365 is not required but recommended for the best experience.

Can I use state abbreviations?

Yes! You can use either full state names (e.g., "Texas") or 2-letter state codes (e.g., "TX"). Both formats work.

What does automatic fallback mean?

When you query historical data that isn't available, the function automatically returns current rates with a notice row instead of erroring. This ensures your formulas never break.

Do spill arrays work in Excel 2016?

Dynamic arrays (spill) require Excel 2019+ or Microsoft 365. Excel 2016 users will only see the top-left value. We recommend upgrading for the full experience.

Pricing

Excel Add-in integration follows the same pricing as the REST API:

Get Your API Key View Full Documentation 📥 Download Test Template