Phone number at checkout: required, optional, or SMS opt-in?

Make the phone number optional and separate it from SMS marketing opt-in. Required phone fields cost conversions from privacy-sensitive shoppers; a clearly optional field with a stated purpose, delivery updates, captures most of the value with almost none of the abandonment.

Why the phone field is radioactive

Of all the checkout fields, the phone number provokes the strongest reaction. Shoppers will hand over their email and address without a thought and stall at the phone field, because a phone number feels personal in a way an email does not. It implies calls, texts, and a direct line to their pocket.

The data backs up the feeling. Phone number fields consistently show higher abandonment and higher fake-entry rates than any other standard field. Shoppers who do not want to provide it do not just leave it blank. They enter 555 numbers, which then pollute your SMS list and your delivery notification system.

Required phone: what it actually costs

Making the field required is usually a shipping or fraud decision, not a marketing one. Carriers want a contact number for delivery issues, and fraud systems score orders with verified phone numbers differently. Those are real needs, but they are not every store's needs.

If you require it, measure the cost honestly. Compare completion rates for sessions that reach the phone field against your other fields, and segment by new versus returning customers. New customers are where the requirement hurts most: they have no relationship with you yet, and the phone field is where that absence of trust becomes concrete.

Optional with a stated purpose wins

The best-performing pattern is an optional phone field with a one-line explanation of what it is for. Delivery updates only is the highest-converting framing, because it answers the shopper's real question: what will you do with this. A field with a purpose gets filled. A field without one gets skipped or faked.

Keep the optional field visually optional. A small optional label next to the field name is enough. Do not preface it with a paragraph of reassurance; that signals that there is something to be reassured about. One line, plain language, next to the field.

Separate the number from the marketing opt-in

The damaging pattern is combining the phone field with SMS marketing consent: one field, one checkbox, and the shopper cannot tell whether giving the number signs them up for texts. This confusion suppresses both the phone number capture and the SMS opt-in rate.

Split them. The phone field is for the order, with its delivery-updates framing. The SMS marketing opt-in is a separate, unchecked checkbox with its own clear language. Unchecked by default is not just compliant in most jurisdictions. It is also better converting, because shoppers who opt in deliberately stay subscribed longer than shoppers who were nudged.

Validate gently or not at all

Phone validation is where good intentions go to die. Over-strict validation rejects valid international numbers, formats the shopper did not expect, and VOIP numbers that are perfectly good contact numbers. Every false rejection is a shopper you told their own phone number was wrong.

Validate format loosely, accept international formats, and never block submission on a phone validation failure for an optional field. The phone number is a nice-to-have contact channel, not an identity document. Treat it that way.