local currency requirements?/

Credit and debit cards will work - Visa or Mastercard is best. American Express and others have limited acceptance.
For small amounts, cash is better. You can easily get cash from an ATM using your debit card, Norwegian Krone, Swedish Krona, Danish Krone or Euros. Make sure you have told your bank you will be using your cards outside your home country, otherwise their fraud system may block your card.
You may need to buy special cards to use local transport. This is particularly so in the Netherlands. I am sure someone else will fill in that gap.
Tipping - simple rule don't. There are some places where some people tip, but it is never compulsory.

Thanks .
Are Norwegian Krones interchangeable and usable in Sweden and Denmark ?
If yes, then may be no need to have local cuurency for all.

NOK, SEK and DKK are not interchangable. While the Danes use to rule their northern neigbhors, they are independent countires.

Always good to have the appropriate coins for coin-operated WCs. That said, credit cards are widely accepted and cash needs are minimal.

Tipping in Norway is optional. Wait staff are paid living wages. That said, with good service, a tip is appreciated by staff with round up to 10% being appreciated. With credit cards, the machines are brought to you and your card does not leave your sight. Card machine will ask if you want to add a tip.

The three K's not only are issued by different national authorities, they also don't have the same value. At https://www.oanda.com/currency/converter/, you can find that one US dollar currently buys you about 6.29 Danish Krone, 7.99 Norwegian Kroner, or 8.74 Swedish Krona.

Nordic cashless society:
https://www.reuters.com/article/us-nordic-cashless-idUSKBN0KI1AA20150109

Non-EU members Norway and Iceland are also among top users of cards
worldwide, their central banks say.

Swedes often make the smallest purchases, such as for chewing gum,
with a credit card and can use the Swedish banks’ jointly-developed
smartphone app Swish to repay a small debt to a friend. Another app
allow drinkers to buy beers in a bar without queuing.

In the Stockholm subway, it is impossible to buy a ticket with cash,
while some unemployed people selling street magazines now a accept
electronic payments.

I just got back from the RS Best of Scandinavia tour sandwiched between Amsterdam before and after.

This is a list of those locations in descending order from most cash used to least.

I got € in Amsterdam primarily because my B&B preferred cash. I mostly used cash there.

I got SEK in Stockholm, but not very much. I did use cash there a little and the last 50 SEK was used to pay the bus driver for the drinks he provided -- all bottled water for me.

I got DKK on Ærø (Denmark) only because I needed to do laundry and the machine only took 10 DKK coins. I used some cash at the grocery store. I have some coins left.

I got no NOK at all in Norway. Everything was by credit card.

I used flat chip and signature cards, VISA credit card for purchases, MasterCard debit card for cash. I first tried a raised VISA debit card from a different credit union to get € in Amsterdam, and the bank cash machine in the airport absolutely would not take it. There was no swipe option. That credit union remains so far behind the technology, it's pathetic.

Scandinavia is almost totally cashless, and signing for the purchase was rarely required.

As others repeatedly say, Amex is not worth taking to Europe because it is so rarely accepted.

I recently spent a week in Denmark and a week in Norway and never used cash.

Lo, sorry i dont understand. Are you saying the atm was behind the times with technology because it didnt have a swipe option? Isnt it the other way round, having the swipe option is behind the times? Cant remember the last time i saw an atm with a swipe option. Appologes if i have miss read this, its early!

caro, I think Lo was referring to her own credit union (the issuer of the card that the machine would not take).

Laura, i agree, just could be read both ways!!!!

Always have some cash with you. Found that out in Wales a few weeks ago when ordering a late lunch in a Pizza place in Betws-y-Coed. The staff said the card reader was not working? Don't know if that was true or not, but we paid for the meal with cash.

Minor asterisked exception to Edgar's comment above. There are rare instances where one can pay in one currency and get change in another. E.g., I traveled on a Danish-flagged ferry (DFDS) last month; paid for my beer onboard in NOK and received the change in DKK.

RE: There are rare instances where one can pay in one currency and get change in another.

Yes, in boardering countries, merchants may often accept the foregn currency of their neighbors. Another example, Candians boardering the US will often accept American US Dollars at parity to Canadian dollars and give you change in Canadian dollars at parity. However, it would be rare for an American business to accept Canadian dollars so Candians should keep their Loonies in your pocket while in the US.

Here in Switzerland there are many places in border and tourist areas that take Euros. The rule is notes only, no coins, and all change in Swiss Franks.
Larger places (supermarket chains, SBB) have the rate programmed into their till daily. Smaller places (cafés, street food), just use €1 = 1 Frank (today's rate: €1 = 1.16 Franks). Since they have to total up the Euros, pay them into the bank separately and pay bank charges, that is reasonable.

Sorry for the confusion.

Yes, it's one of my credit unions' card technology that's behind. The 1st of the 3 cash machines I used would not "eat" an embossed card and there was no way to swipe the card the old fashioned way. I didn't bother to try the embossed card on the other 2 when I saw no swipe capability on them either.