The single mum's internet provider had debited her account a week earlier than expected, leaving her a little short in paying for her shopping - toilet paper, lunch for her two children and food for her foster kittens.

It was peak hour at the supermarket and, panicking, Ms Crispin dropped some of her groceries as she rushed to determine what she could do without. Then Hamish Flanagan stepped in.

"He just walked up and pulled money out of his wallet and said ‘Here, use this’," Ms Crispin, a disability pensioner, said.

"He didn’t know anything that was going on, it was just amazingly kind."

Mr Flanagan, a 20-year-old full-time Woolworths employee who was manning the self service checkouts on Tuesday, said he didn't think twice about stepping in to help a stranger.

He'd noticed Ms Crispin's groceries carried discount price tags and recalled his own single mum working hard to make ends meet.

It was the Charnwood way, Mr Flanagan said.

“Everyone at Charnwood, we all pitch in when we have to and when we want to," he said.

“It’s a very good community. We have a constant amount of regulars that come in and we always have a really good chat and a joke here and there. It’s just a great place to work, really."

Ms Crispin posted Mr Flanagan's act of kindness to the Canberra Notice Board Facebook group where it sparked a lively discussion about other acts of generosity in the ACT.

One person lauded a Woolworths Dunlop employee who had loaned a shopper money to get dinner. An off-duty police officer was praised for paying for another person's groceries.

Ms Crispin said she taught her 12-year-old son and 10-year-old daughter to be kind to everyone and had hoped her story would inspire others to do the same.

"It doesn’t take much to be kind, even if you’re having a bad day," she said.

"I think the world would be a lot happier if people helped each other a bit more and weren’t in such a rush to do everything and actually looked out for each other."