UPDATE: Kmart no longer doubles coupons on a weekly basis.

In order for your coupons to double at Kmart, you must purchase at least $25 worth of groceries, health or beauty items. This $25 total is before coupons, so your out of pocket can and should be less with your coupons. Kmart only doubles the first 5 coupons up to $1, so hand the cashier the $1 coupons that you’d like to double first (rather than handing them a $0.50 or $0.75 coupon, for example). Your $1 coupon will double, taking off a total of $2 for each item!

Here is how your receipt should look like with the Double coupons taken off:
Kmart Double coupon receipt
Your $1 manufacturer coupon should read:
MFR Coupon $1.00 -F

And the double coupon should read:
MULTI Coupon $1.00 -F

Always double check that you see this MULTI COUPON line, otherwise your coupons may not have doubled!

Kmart currently does not have an official coupon policy posted.