If I am not mistaken, all transactions via the Target Debit card are converted into Electronic Check Drafts. Different banks handle Electronic drafts in different manners. This conversion to electronic draft is what usually results in the "float time" on each transaction. Target applies the same algorithm to allowing your Target Debit transactions as it does with your check writing. I do not know if your combined check writing and debit card use would result in a decline of a transaction....
I know there used to be a series of "levels" with writing checks to control risks where you moved through the various levels.... Don't remember the amounts, but something like 3 checks in a 2 week period for less than $200 that clear ok moves you to lv1...then 5 checks for between 200-500 in a month moves you to lv 2.... then 8 for between 500-1000 made you lv 3 and the glorious top tier was lv 4 where you had no check limit but an upper 30 day rolling limit of $2500. If you had a transaction declined then you were bumped down to the next level and had check writing privileges suspended until you honored the NSF.
I am fascinated/mystified by the details of how the two systems and their interplay or lack thereof.
Once, a guest tried to make purchase with her new Target check card of nearly $120 and asked for $40 cash back. It was declined. I wondered if the purchase amount was too large for the first time. I asked her if she had any cash at all to reduce the amount needed from the card. She answered in the negative. She then tried without the cash back and the check card was declined again. I called a team leader over to see what I could do.
He allowed me to give the 5% discount (I seem to sometimes get inconsistent answers on this at my store, but I have always given at least an apology coupon) and he suggested that she use her regular bank card. She said it was in her other purse and she would have to leave to get it (I did not catch whether she meant it was in her car or at her house, or if she even remembered). Well, I find that at least half the time when a guest says he/she must leave and return with ID/payment, the guest does not return.
My mind then jumped to the reflexive question I always ask a guest when I am trying to convince a guest to open a red card: I asked if she had a check. She was confused, but eventually answered that her checkbook was in the purse she had with her. OOPS! I thought. The system will decline her check for the same reason as her check card and she will be inconvenienced further and never want to shop at Target again.
I reconfirmed that she had no cash at all. I took off the 5% (subconsciously rounding up a little, since I felt bad about all the inconvenience she faced simply trying to use a program we advertised to get 5% off). She wrote the check for over $112. I crossed each finger as I fed the check in. I expected to see a decline, but after first swiped her Driver's license (preceded by a brief but heart-stopping search for it) THEN keyed her DL#, the little dog appeared with with a thumbs-up.
Maybe I felt too emotional, but I always find it very awkward and embarrassing when a guest does everything right in using a program I must promote constantly and then he or she is almost unable to use it based on something I am not supposed to advertise.