If they haven’t "forgotten", they’re far too tired, have an important something else to do or a vital contact to make. The list of excuses is endless.
To be fair, they do forget at times, like we can mentally put aside something we’d rather not get on with. And thinking about a chore can also be very tiring! And they do need to text their friends - after all they haven’t seen them for at least an hour.
The solution, then, is the dreaded list, perhaps affixed to the fridge. A list to be referenced at key times of the day - straight after school, before dinner, before heading out.
If we’re teaching about sharing the workload and responsibilities, then we have to give some responsibility as to when things get done and what they need to put aside for the moment.
Instead of "right now" negotiate the timeframe - "sometime before dinner", "after your practice", or "before you go out".
Then follows the natural consequence if the chore hasn’t been done - dinner isn't kept warm, the Wi-Fi goes off, clothes left in the bedroom aren’t washed, the car is unavailable until washed as agreed. You’re not refusing to feed, launder or transport, just going with the prearranged outcome.
It can be inconvenient. It takes effort to pleasantly shake awake a teenager who, you’ve just remembered, forgot to bring in the washing or put the bins out before going to bed. No lecture, no blame, just a friendly reminder. Extreme, yes, but necessary if you’re attempting to establish consequences.
Try to be positive. Speak in terms of what can happen once the chore is done rather than what can’t happen until it’s done. "You can go out when the dishes are done." Sometimes they won’t mind missing a meal or staying in, so you might have to keep a meal warm the next day, too.
Initially, there’ll be anger, sulks, begging and promises - "Please, please ...", "I promise to do it tomorrow", or "This is dumb". Don’t be tricked into arguing whether it’s fair or whether other kids have to do it or react to being mocked. Just quietly keep repeating the arrangement - "You can go out when the job is done." Talk about any abusive language later.
It’s not the severity of the consequence that matters, but the certainty of it. If it’s happened just as you said once or twice, the odds are that they’ll understand that this consequence will always happen. You say it, you mean it, you do it.