offering to help with a credit card bill

Personally I would rather owe money to a credit card company than to a friend or relative. They know that they can ask you for help if they need to but as long as they are not falling behind on the interest payments, it is not really a problem.
They know they can ask you and it is to their credit that they want to sort it out themselves. Maybe if there is a birthday coming up, you could ask if they would prefer money to a present and give a few hundred but otherwise, as everyone else has said, leave it to them.

Do nothing. It is their business.

They are adults, capable adults who need to run their own lives without interference.
Why do you want to do this?
I suspect (given your remarks about your daughter-in-law) that it has something to do with control masking as 'kindness'.
If they needed financial help they would've broached the subject. Leave well alone and reflect carefully on the reasons why you blame DIL and not your son for the debt.

Say nothing. If you keep bailing them out they will never learn to budget. I have a friend who constantly "helps" her daughter and son-in-law, they are both in very well paid jobs but never bothered budgeting because my friend was always there in the background. They have now run up huge debts and my friend is now considering selling her house in order to "help".

Thank you all! Your words are wise and kind - and on re-reading, I can see it sounds as if I 'blame' my DiL - I didn't mean to, but it is interesting to see that through your eyes (I edited a longer post!)
She is a lovely girl and a wonderful mother, and we get on very well. I see this as one of her 'faults' in the round (my son's 'faults' weren't relevant to this post!). But I do think that in considering this, I must take account of how I may come across.
I take the point about 'being left out accidentally' and should add that the paperwork wasn't financial - this paper was just among others.
After typing the original post, I was sure what the replies would be, but posted anyway, and am grateful for Gransnet at its best.

I'm not with the majority on this. The amount involved with accrue with high interest, unless they are paying large amounts towards it each month ie more than the amount asked by the credit company. I would not blatantly offer the money but perhaps bring the high interest rates charged on CC debt and that surely if anyone needing a large amount of credit would look elsewhere first eg family who would probably not charge any interest. Make it a general conversation, they may well ignore and not approach you later which is fine. At least you will have laid the ground for them to approach you. After that, leave them to deal with by themselves.

Say nowt and keep out!

As Purpledaffodil said there are lots of 0% deals over as long as 32 months. It may already be one of these. Don't say anything - my mother-in-law has been stressing over the idea of my daughter's 0% deal unnecessarily and causing friction. My daughter has divided the debt into chunks and will have paid it off as the 0% expires. She was told by a bank that servicing the card this way (regularly) improves her credit rating.

Keep quiet.

And continue to be ready to help non financially.

Our son ran up a debt with us that we had to forgive, and to be fair to his two sisters we gave them the same amount he owed stating the reason why.

Since then he’s become a financially responsible adult.

Say nothing. Being a poor money manager and a bit daffy doesn’t make anyone a bad person. Likewise being a good money manager and cutting your coat according to your cloth a good one. Stop blaming your DIL

Say nothing - hold onto your cash. You could have a little "unrelated" rant about the younger generation and debt but it would probably be too obvious. Down the line they may be in real trouble and come to you, then play by ear.

Is it likely they gave you the papers in the hope you would see the debt and offer to pay?

At some stage in their life we need to let our children sort themselves out.
If they wanted your help they have had the opportunity.
They are grown ups and are sorting out things in their own way.

I'm sure its right to keep quiet. If at sometime in the future you are approached then is the time to think about it.

Keep quiet and don't look at their finances again! Better off not knowing it's their debt their business!!

I think a lot of young couples have debts nowadays. What we have said to our son and DIL is that if they ever get into difficulties with their finances, to come to us before they get themselves into dire straits. And we will help. Perhaps you could tell a wee white lie and tell them you have been speaking to a friend whose son and wife have got themselves in to a lot of debt which is just getting worse. Say that you'd hate to think of them worrying about money and if they ever find themselves in difficulties, not be embarrassed, but please come to you and you will help because you know how hard it is for young couples these days.

No, say nothing and put it out of your mind. If you are too generous and ready to help out they won't learn to manage their own finances.

I agree with the majority, keep out! Remember too that they may have transferred their debt to a zero-interest credit card.

leave it at one point my oarents helped me out financially with debts that i never learnt to stand on my own two feet , i have bipolar and spending is my release to the point of almost losing my home at which point they couldnt help me i had to get mysrlf out of it through an iva , i appreciated the help they gave me but i never learnt to manage money myself as i new i could fall back on them

They are adults who work.

Getting into debt is something they need to think about, and paying off their debts is also a grown up thing to do. Let them learn to manage money.

So many of my children's friends, in their 30s, run to the bank of Mum and Dad when they need things or a cash boost. I may be speaking from the perspective of a woman who had to earn for herself every penny she had, and never had handouts, but the tough times are teachers.

They may become better managers of money if you stay out of it. Going without a few luxuries for a while, so they prioritise the repayment of debts and the way they spend money is a lesson they really need to learn. They will survive.

Say nothing. Plus I am sure they wouldn't like the burden of owing the money to you.

The best way for them to learn how to manage their finances is to sort it out thmselves.
My other thought is was the bill left in view accidently on purpose in the hope you would make them an offer. If so and you paid it for them do so on the basis there is a formal representative plan

Stay out of the finances of others is my advise.I know to my cost how it can cause problems within a family .

3 times we ‘helped’ our son by giving him interest free loans and paying off a debt. It changed our relationship for a while, and a simmering resentment cane to a head one summer when we were camping uncomfortably in Dorset & heard that he was on holiday in South France, while stil owing us money. The anger I felt was extremely damaging & we realised that ‘neither a borrower or a lender be’ was absolute sense. It changes relationships, & prevents our AC from becoming true adults. Their generation don’t feel bothered about debt the way that perhaps we do, & we don’t need to know about their financial situation.

I agree wit the others.
My husband gave our d-i-l £2,500 for some urgent work to be done on their kitchen. They spent the money on a motorbike!
Lesson learnt.