I was the tagalong friend last week. Separate transactions, I used my own debit card but they scanned my friend's costco card for each transaction (there were 4 of us, only 1 was a member).

Do self checkout and go through twice.

My brother was not allowed to use his card for purchases on my membership at Costco. I had to use mine and he reimbursed me.

A Costco cashier told me that the name on the debit card needs to be one of the names on the Costco membership.

You need to get your membership card scanned at checkout, but the purchase is not tied to your card. Your friend can use his/her own debit or ATM card.

Call costco

I thought all transactions had to have a membership card. Otherwisr, it would be open to everybody.

Costco makes most of their profit on membership enrollment so it doesn't make sense for them to allow non members to make purchases.

Cash or their Am Ex card (although their agreement with Am Ex is coming to an end soon).

Your friend can pay with their own debit card. I've gone & paid with different cards before. It's not like your Costco membership is linked to a specific bank account.

9:46 - if you give them a gift card, do they need to go with a member to get in? What about checkout? Do they charge a premium for non-members?

You can buy them a gift card from Costco and they can go anytime by themselves. They pay you for the GC of course.

I'm pretty sure I've always used my own debit card when I've gone with a friend.

They cannot use their debit. Two transactions. Have them pay cash.

They will do separate transactions for each, but will need to scan your membership card for your friend's purchase. Not sure about the debit card thing as I only use credit cards.

It has to be under your card. They can't buy anything without a membership. We took friends and paid for their stuff and then they just paid us.

I know you can shop with a friend but can they use their debit card? Will they do separate transactions or does it need to be under my card?