Is this a venial or mortal sin?

[abbachild17]

I’m a new Catholic and still not always sure what is venial or mortal. I know the three guidelines that are used, but still somethings are fuzzy to me.
About 1 month ago, I left Walmart with my groceries and while putting them in my van, realized that they didn’t charge me $3.96 for the case of water I had bought. It was under the cart. Being overweight and tired and hot, I decided that I did not want to walk all the way back into the store to let them know. Plus, I needed to get home since my kids would be getting off school soon. I thought I would just go in another time or just send them a letter.
However, now I have never done that. I still feel bad about walking about with the water and not paying for it.
What should I do? Is that venial or mortal? I’ve asked God to forgive me but still don’t feel peace about it.

 

[Fr.Vincent_Serpa]

Dear Sonya,

It is neither. If you had noticed the error at the checkout stand, then you would have been obliged to say something. But this is not the case. You are not obliged to inconvenience yourself over a few dollars because of their mistake.

Fr. Vincent Serpa, O.P.