Superannuitants are being encouraged to be more assertive in asking for SuperGold Card discounts they are entitled to, as many are missing out.

A SuperGold Card discount was offered by hundreds of small and big name businesses in New Zealand, but a lack of promotion meant many older people were unaware of the details.

The Warehouse Red Sheds offer a 5% SuperGold Card discount on the first Tuesday of the month, but an older couple with a trolley full of goods left the retailer's St Lukes store in Auckland today without their discount.

"Oh well. Next time," The Red Sheds customer Marcia said, as she loaded up her boot.

Still, she was persuaded to go back to the store and ask for the discount, and returned a few minutes later $18 better off.

"We got $18 out of the SuperGold discount," she said with a broad smile and an armful of canned food items. "So we've just bought… some extra bully beef, spaghetti, and... a bit of fruit salad."

The Warehouse Red Sheds offers a 5% SuperGold discount on the first Tuesday of the month. Photo: RNZ

She said The Warehouse apologised, which was followed up with a response from the head office.

"We really appreciate this being brought to our attention and we're sorry the couple didn't get the discount they were entitled to the first time around. It's highlighted a gap in how we provide value to our customers - and we're looking at how we can make our offers more visible," a spokesperson from The Warehouse said in a statement to RNZ.

The promotion of the SuperGold Card was something concerning to other shoppers.

A shopper outside the Point Chevalier Woolworths, Frances Marychurch, also raised concerns about the lack of awareness.

Marychurch said she only used her SuperGold at Woolworths and was unaware she could use it across the street at the New World supermarket.

"So I find it's very difficult to find ways to use your gold card. The ones that are supposed to do it, don't ask you for it," Marychurch said.

New World shopper Ross Horne said: "Personally, I think it is not actually publicised enough. Occasionally you'll see a store with the sticker on the door, with the gold card."

Mike Matthews, general manager of Communicare, which offers community support for seniors, said businesses should do more to promote the SuperGold Card discount, though superannuitants also had a role to play.

"I think that you could have some corporates take a real leading role in terms of stepping up to do this. But also equally, I think the superannuitant community ... you know, use your feet, and that will encourage those who do support (discounts) and give them the benefit of additional business," Matthews said.