What do you do when your child won't take no for an answer?

In this instance, I would raise my voice and shout.

"If you ask for X again, you won't get it."

"If you ask again after that, it goes in the bin"

'I said "yes, in a minute". One more demand and that answer will change to "no". '
And follow it through.

Nagging for something I've said 'no' to - that would be a 'Go to your room and don't come out until you're prepared to behave better.'

With the delayed time one she needs more obvious way of timing/knowing at what point it will get there because the "minute" or unspeficied amount of time doesn't mean anything to her - or she needs to be given a task to help get the snack drink ready ie fetch plates or bowls or cups.

Though sometimes I thought it was just they wanted attention - so were competeing with task I was doing at the minute - but then the obvious clue they can see hear to end of that task or time I was giving that task helps - timer/clock end of TV program - or being given a task to do to distract so you can get it done.

Though at 7 a complete stop everything and look at them giving them your entire attention and saying I need to get x done first and longer you distract me from it longer it will be till I can do anything for you. Then suggest a distraction activity to them or get them to acknowlege they need to let you have the time before restarting task and let them work out what to do till you have time.

Though I am wodnering if you get talked at and asked same questions for facts with no pause to take answers in - DS did that drove me mad at times but it was more than pestering to make me change my mind - it was more aimless and anxiety driven that that.

Agree with @outerspacepotato chores are a good time filler for kids who are waiting for something and won't leave you alone, or for claims of boredom.

They keep bugging, it's Chore Time.

If it's things like snacks or drinks, I had a fruit bowl on the table and a 7 year old can get herself a glass of water.

Our kids learned very young that my "no" meant "no." If they persisted, they were told they had their answer and, if they didn't stop, the next thing they wanted would be an automatic "no" so they could learn how to take it appropriately. Usually the "mom look" and a firm "Enough" did the trick once they got past the toddler stage.

My reply was always "I've said no and asking me again and again is not going to change my mind. So you can keep asking or stop, either way you won't be getting X"

Yes to this.

Yeah pretty much this. "The more times I have to stop what I'm doing to answer you, the longer this is going to take" on repeat.

Or just ignore after the first few times. DH puts earplugs in

We don't generally give a negative consequence as, for us, if DC are doing this then they've got to the 'any attention is good attention' phase so ignoring seems to work better.

And as pp have said, never ever cave in as it just reinforces the behaviour.

I try to give specific answers rather than just say no, it seems to help.
For example: DD - can you play this with me?
Me - I need to finish these two jobs which will take about 10 minutes and then I will.
She usually accepts this but wouldn’t let me get away with it “in a minute”!

After you've said no once, the next answer is "Are you asking again? I've already said no, and if you ask again, you'll get a time out." She earns a ten minute time-out every subsequent time she asks even if she ends up spending hours in time out. After the time out she needs to apologise for not listening.

Don't address the request itself after you've said no the first time, in other words.

By the same token, make sure you think a bit before saying no - it shouldn't be the default.

This is a very good idea.

There's no need.

Longer answer is giving consequences can create a drama some are attracted to, as a pp mentioned. Alternatively it can just worsen a situation unnecessarily.

In general, I don't give consequences or sanctions (or rewards) bar the rare time or even rare threat to use them. This approach has worked v well (two v different dc 10 and 13). One of them was v tricky and the other never had to be asked twice, told twice and never even had a tantrum as a toddler.

I had one very persistent child-

So I would say "no you can't light matches (or whatever) and please do not ask again. If you do ask again you will forfeit X" and so on. Realistic penalties that you have to enforce-commersuarate with the wrongdoing.

If you are clear up front what the penalties are for repeatedly asking then it feels more like the child's choice and once you are enforcing the penalties they will see the cause and effect and hopefully learn.

Bearing clear and consistent for the win.

Children can become "consequence blind", but lack of attention (and lack of what they were begging for) is a fairly good consequence.

Buy her a timer or set a timer for her saying you will be there in 5 mins but if she keeps asking you to come now explain it will take you longer to finish what you’re doing before playing.

I guess the problem is she knows if she wears you down, she'll get it

Well, hang on a minute, you are literally changing your story , even on this thread.In your OP you said
'It can be something I've said no to or something she wants immediately and will not stop keeping on until she gets.'
It is no wonder your daughter doesnt know where she stands with you.

That's because children know you don't actually mean in one minute and that you mean at some indeterminate point in the future when I can he bothered standing up/when this programme has finished/when I've done this job.

It feels like a fob off because it is.

Give a more definite time if you actually intend to give it to her, eg I am just doing X right now. When I have finished I will get you Y.' Or "This will be finished in 10 mins so I will get that for you at 4 o'clock".

Why can you only play or get it in a minute? What is special.about that minute? Is it really a minute or is it longer. Be more specific.

I think you need to be more specific.

If it’s 1pm say you can have the snack at 2pm and you will let her know when it’s time or set a time or your phone/help her learn how to read a clock.

I think saying in a minute is setting yourself up to fail because she will of course keep on asking.

Wait, what? Why are you taking things away from her? She isnt being naughty, she is doing what you have literally trained her to do! You are the one who is in the wrong for sending mixed messages and teaching her 'no' means 'yes'. You are punishing her for your own weakness!

The first time you say no, and why it is is a no. The next time you say no, i have already told you why, and after that you just ignore.

This highlights what I was about to say quite well.
Lots of children the conversation would be like the one above. For some children (looking at you DC number 4) never ever ever give up. They ask the needle they plead they don't care if things are removed, they don't care, if they get sanctioned. My youngest was born like this. When I was trying to wean her off the boob at 16 month she asked to be breastfed for 12 hours straight. She is like this about everything when she decides she wants it. It's properly exhausting.

This. Never give in and if it persists you need to up the stakes. At 7, mine were told that if they kept asking for more X, there would be none if it tomorrow. I said it stop it now, or else … basically.

If you gave given in before, then that is why she is trying to wear you down. Because it worked.