Building a Client-Side Invoicing Engine & Statutory UK CIS Calculator in TypeScript

Handling statutory invoicing logic inside browser-native applications often requires complex compliance considerations.

When building Invoicycle, we separated two statutory calculation routines into standalone, zero-dependency open-source packages:

1. UK Construction Industry Scheme (CIS) & Domestic Reverse Charge (DRC) Under Section 55A VATA 1994, reverse charge VAT shifts the tax accounting obligation to the contractor, while CIS deductions apply strictly to the labour component.
2. Interactive Web Tool: Invoicycle UK CIS Generator

3. GitHub Repository: invoicycle-uk-cis-calculator

4. Statutory Late Payment Interest & Compensation
   
   Governed by the Late Payment of Commercial Debts (Interest) Act 1998, UK businesses have the legal right to claim statutory interest (Bank of England base rate + 8%) plus fixed compensation charges of £40, £70, or £100.

5. Interactive Web Tool: Late Payment Calculator

6. GitHub Repository: invoicycle-late-payment-calculator

Both calculation routines run entirely client-side, ensuring business financial records remain private and secure without external server dependencies.

Explore the open tools and templates at Invoicycle.com.