Contributions from (pensioner) MIL to household

I'm not up to date with benefits but have you looked into Carers Allowance?

And yes she should be paying more than £400 pcm

Do you know what has happened to the assets from her house sale? Just sitting in the bank waiting for the new inheritance tax wallop that's undoubtedly on the way? Does your wife/partner have POA if she is incapacitated even further. Does she have other children besides your partner? This has the potential to get quite messy especially when you or her feel you are being taken advantage of.

What she is currently paying as bed and board is one thing and the value/cost of it could be argued ad nauseum, but she basically moved in with you on one pretext and has reneged on the bargain.

What is the position money aside if her care needs rise significantly? What was discussed with her before she moved in? Are you claiming carers allowance?

If you really want to push the point then I would find out the cost of an assisted living or indeed care home. if her pension income [which would stop after her death anyway] will cover it, it sounds like it would be better for relationships all round if she was asked to consider the option. She'll either seriously consider it, or reassess the value for money deal she is getting now.

As for DSD, she is presumably not being waited on hand and food or being ferried about.

this second option is great.

or just lie and say dd is paying the same. technically she would be anyway for the hours worked considering she requires a lot less care!

Can you show her the figures for her share of all your costs, including fuel, petrol to take her to appointments, TV licence, additional heating, water rates, and a notional rent equivalent to what lodgers locally pay for a similar room? And also show her the figures for what it would cost if she moved back home? I know she may not take in much, but if it's clear it comes to more than £400 it should be clear that her contribution needs to go up.

I think you're actually still being a bit generous and £700 or upward would be reasonable. If she has more than just her state pension and you are providing absolutely everything in terms of housing and food, cleaning and care, then this would still be an exceptionally good deal.
I do agreed with the pp, however who says this whole issue could be clouded by potential dementia.

Not unreasonable at all, tbh even £600pm is a tiny fraction of what her caring costs would be anywhere else.

@PaterPower , have you and your partner discussed with your MIL what will happen when the care you provide is no longer sufficient? More to the point have you and your partner thought about her ever increasing needs?
She may be conscious of wanting to have enough money left in reserve to pay carers when that time comes.
Are you and is she aware that regular gifts out of income are (at present) not part of an estate when someone dies? So no inheritance tax to be paid.
Old people often get a bit fearful because they are vulnerable I suppose. You all need to sit and have a chat.

I think £500 is more than fair, if she can afford it, plus she is family .

I don't think you're wrong to ask for more, but I think you need to be totally upfront about why - not because she agreed in the past, but because that's
what it's costing you to have her live with you. Unless you spell this out she will likely feel that either you're trying to make a profit out of her, or that she's being used to subsidise your daughter.

It may be that in your view her income is good, but to her it probably seems that she has to manage for the rest of her life on whatever she has now, and she's afraid to deplete her resources in case she needs them for health or other care in the future. Someone upthread asked what else she was going to spend it on - maybe £12500 on a new hip so she can stay mobile and comfortable, maybe a few hundred a month on specialised care so she can stay with you instead of having to go into a home, whatever. It also sounds as if the sale of her property was quite recent and she hasn't had time to get to grips with how much her overheads have shrunk.

I would approach it on the basis of finding a contribution that's fair and reasonable to everyone, rather than you imposing your idea of what it would be reasonable for her to pay. You need to at least listen to he side of things. It doesn't have to be confrontational as you seem to assume, it's more about working out a way forward that feels acceptable to everyone, which after all is pretty important if you're all going to be living together without building up some resentment somewhere.

I would definitely get it sorted before the winter and calculate what having her living with you will cost as I presume the heating will need to be on all day for her when you might have just left it off for yourselves.

Carers locally are charging £35 per hour, £40 at the weekend. She's getting a bargain. You really shouldn't be out of pocket. £600 is still perfectly reasonable.

Gosh, how nasty of her to compare her situation to that of a young adult just starting her life.

A parent and a child are completely different AND you had an agreement in place she is backing out on.

I would just sit down and say this is what you need to pay a month, or you have 3 months to find a new place to live.

She isn't worried about taking advantage or emotionally manipulating you both and she sounds deluded/ungrateful about all you do.

You need to be a team and lay down some boundaries as in reality this could go on many years.

I think as harsh as it may seem you will just have to be blunt!

Another vote for upping the amount - £400 is very little nowadays.
It's also irrelevant and none of her business what the DSD pays.

Price up a suitable 'assisted living' alternative for her and then present the two as options - the new external place or yours at £700 a month.

Make it clear that the current arrangement is not working for you.

A couple of things you could do

1. calculate what she;s actually costing in gas, electricity, water etc (default value would be 1/4 total bill), petrol, and your time (at minimum wage).

2. pt the rent up for both of them (then quietly tell DSD you're putting x amount into a savings account for her).

If she didn’t have your and partner's help would she need carers in twice a day? My friend’s mother has three carers in £75 daily,£100 weekends and bank holidays. Base her payment on those lines. These are costs in possibly a cheap part of the Uk.