Find why shoppers abandon my online checkout and fix it

Help me reduce cart and checkout abandonment on my online store. Platform and checkout type: [e.g. "Shopify one-page checkout", "custom build"] Funnel numbers: [sessions, add-to-cart rate, reached checkout, reached payment, completed orders - by device if possible] Checkout steps and fields: [LIST OR DESCRIBE EACH STEP] Shipping: [costs, free-shipping threshold, delivery estimates, and where they first appear] Payment options: [cards, digital wallets, buy now pay later, PayPal] Payment decline rate: [IF KNOWN] Guest checkout allowed? [YES/NO] Customer comments or exit-survey quotes: [IF ANY] Recent changes: [new apps, theme update, price change, fraud tool] Check against common causes: - Surprise costs at the end (shipping, tax, fees shown late). - Forced account creation, too many fields, no address autocomplete. - Missing preferred payment methods; card declines or failed authentication. - Unclear delivery date; returns policy hard to find. - Mobile problems: wrong keyboard types, small tap targets, slow pages. - A discount-code field that sends shoppers off to hunt for coupons. - Missing trust signals near payment. Return: 1. The step with the biggest drop and the most likely causes, ranked by the evidence. 2. A fix list: change, expected effect, effort, how to measure it. 3. Two A/B tests to run first, each with a success metric. 4. An abandoned-cart email and SMS outline (timing, content, incentive or not), sent only to shoppers who consented to marketing messages. Base the diagnosis on my numbers. Where data is missing, tell me exactly what to pull.