Tax-exempt resale cert workflow per state (CA, NY, TX, FL), how is it managed?

Every contractor reselling materials needs a state-specific resale cert, and the rules vary wildly:

• CA BOE-230, Resale Certificate. Permanent (no expiration) but must be on file. CDTFA audits aggressively.
• NY ST-120, Resale Certificate. 90-day blanket or single-purchase variant. Permanent if on file with correct sales-tax registration #.
• FL DR-13, Annual Resale Certificate. Issued by the Florida DOR each year. Must be re-uploaded annually.
• TX 01-339, Texas Sales and Use Tax Resale Certificate. Permanent if on file with a valid 11-digit comptroller’s sales tax permit #.
• IL CRT-61, Illinois Certificate of Resale. Permanent.
• OH STEC-B, GA ST-5, MA ST-4, etc., each state has its own form + rules.

Magento implementation: customer-attribute model stores per-contractor {state, cert_file, cert_number, issue_date, expiration_date}. Cert upload during account registration; auto-flag 30 days before expiration. Avalara CertCapture ($5k, $25k/yr depending on volume) handles collection + validation across all 50 states, chases contractors for missing certs, validates state-by-state rule changes, keeps the audit trail. TaxJar Plus handles the tax-exempt rule enforcement at checkout (no tax charged if valid cert on file for that state).

The state sales-tax audit is when this pays for itself. Auditor asks for the cert backing every tax-exempt sale in a 3-year window; if you can’t produce it, you owe back-tax + penalty + interest. I’ve seen yards owe $400k after a single audit because cert collection was on a clipboard.