Wallex Wallpapers: Business Invoice Option at Checkout (Frontend, Email and CRM)

We're looking for a full-stack developer to add a business-invoice option to the checkout flow on our wallpapers e-commerce website. Fixed price of $50 USD, paid as one milestone on completion. At a high level: during checkout a customer should be able to ask for the invoice to be issued to their company, and the business details should then flow automatically into our order email, our CRM, and the final invoice. What needs to be done (high level): 1) Checkout page (frontend): Add a checkbox that, when checked, reveals two required fields for business name and business tax ID, with basic validation (the tax ID must be exactly 9 digits). When unchecked, the fields are hidden and not required. Labels are in Hebrew and will be provided. 2) Order confirmation email: When the business option is used, include the business name and tax ID in the order confirmation email so the orders team has the details right away. Otherwise the email goes out as it does today. 3) Server-side CRM and invoice integration: On the website server, where the existing CRM (Kaveret) API calls already happen, update the customer record with the business name and tax ID (for both new and existing customers) before the invoice is generated, so the invoice reflects the business details. The exact field mapping will be shared. The whole flow must work with no regressions when the business option is not used. A short call will be held before starting to walk through the exact details, field names, and screenshots. Deliverables: - The three changes implemented and tested on our existing site. - Light end-to-end testing of both the business and non-business checkout paths. Timeline: roughly 4 to 6 business days. Revisions: up to 2 rounds within scope. Ideal candidate: a full-stack developer comfortable with frontend JavaScript, server-side code, and third-party API integrations. When applying, please briefly mention similar checkout or CRM/invoicing integration work you've done.