My sister has been living at my widower father’s house for regular periods over recent years due to a marriage breakdown, spending the rest of the time in her former family home. My father has said that when he dies, his home, which is probably worth about €825,000, will be bequeathed equally to his five adult children.I am concerned that, after my father’s death, this part-time arrangement with my sister will cause issues for the other siblings in selling the house. I also think (although this part is really none of my business) my sister might have an unmet tax liability for the value of the part-time accommodation she is receiving from my father. The value of this (she also works from there about 10 days a month) is definitely worth more than €3,000 a year. My sister and father refuse to formalise any sort of licence agreement.Do you have any experience or knowledge of how such part-time living arrangements are treated by the Revenue Commissioners for tax and by the law in terms of inheritance? Are there any rights or entitlements that could go with this kind of informal part-time arrangement, akin to adverse possession or right of residence?I fear a situation whereby after my father dies, my sister refuses to leave or support the preparation of the house for sale, or says she wants to buy out the siblings but won’t agree to a market price or commit to a timeline.If my father wishes for all of his children to realise the value of his home equally after his death, what should he do now to ensure this happens?HKFamily break-ups are difficult for everyone involved and can lead to all sorts of complications when it comes to basic issues around living arrangements and the like.Two into one doesn’t go and many couples simply do not have access to funds or a mortgage to buy a second home. Your sister and her ex appear to have agreed a somewhat novel arrangement where the children stay in the family home and the parents alternate their occupancy.But for the rest of the time, she needs somewhere to stay and, while no adult wants to turn the clock back and move back in with their folks, it is certainly nice to have the option available as a fallback arrangement if life does not work out as we would have wished.You have two basic issues that concern you here. First there is any tax implication of your sister’s current accommodation arrangement with your father. Second, you are nervous of what might happen when he dies.The good news for your peace of mind – and indeed that of your father and sister – is that there is no financial implication in her spending part of her time in her old family home. And, for your piece of mind, nor does it create a precedent in terms of adverse possession or right of residence.While the rules governing what the Bank of Mum and Dad can and cannot do have tightened in recent years, there are still exceptions and one of them covers this situation.Section 82 of the Capital Acquisitions Tax Consolidation Act 2003 outlines certain things that are specifically not liable to capital acquisitions tax (CAT) – inheritance or gift tax – nor do they count against your lifetime tax-free threshold.The associated Revenue guide to the CAT treatment of receipts by children from their parents for their support, maintenance or education is really helpful in explaining the legislation in plain English. And it states, among other things, that in relation to the “non-exclusive occupation of the family home by a child (including, where relevant, the child’s spouse/partner) family member, Revenue’s view is that this does not give rise to a gift by the owner of the property to the family member.“Thus, in line with Revenue’s long-standing approach, there is no question of trying to attribute a value to ‘bed and board’ provided by the owner of the house to a child (including where relevant that child’s spouse/partner) of any age.”So, there is no tax implication for your sister in staying in the family home with your father, nor is there any need for any licence or written arrangement to govern the situation. The key words here are “non-exclusive”. If you father was moving out to allow your sister the run of the house, the nature of the arrangement would be different and the issue of CAT on such a “gift” would arise.But what, then, when your father dies?This has the potential to be more complicated. At that stage, as you understand it, your father has planned that you and your four siblings will share ownership equally. In that scenario, the obvious thing is that the property be sold unless one or more of the beneficiaries wish to buy out the others.Without some careful planning, this has significant potential for misunderstanding, discord and even legal bills that would fundamentally swallow all of the inheritance your father hopes for you to have. Earlier this year, the courts ruled on a protracted dispute between four adult children over what to do with the family home of a couple who had died 10 years ago. It was a textbook case of what can happen in the absence of clear instruction and, after a decade of dispute, I imagine the only real winners were the lawyers.Parents assume their children will always get on and reach an amicable outcome but as that case earlier this year and countless letters about wills that cross my desk attest, inheritance can bring out the worst in people.In this case, even assuming the best of intentions, one sister is still going to be relying on that accommodation and you are certainly correct to suspect she might not be keen to leave the home as she might not have other available alternatives.If your father wants each of his five adult children to benefit from the inheritance of his home, the only real way of ensuring that happens without discord is to make very specific provision in his will. You don’t actually say whether he has made a will. If so, it may well need amending. And he should take specific legal advice before doing so to ensure the wording is precise and cannot be misinterpreted or left open to successful legal challenge.That would broadly provide that the property be professionally valued at a certain point after he has died – most likely within a set period of probate being secured. At that point, each of the siblings might have the opportunity within a set time – say three months – to raise sufficient funds at that valuation to buy out the others. It might be one sibling or a group of more than one.In the absence of such an agreement, the property would go to the market and be sold at the valuation price or the closest price below that within a certain time period. There are all sorts of limits that could be put upon it to ensure the property is disposed off – to a sibling or otherwise – with backup provisions in case a dip in the housing market meant expectations had to be tempered.Many of these are things you have considered yourself but it is a very particular set of instructions for a will so the legal advice on the precise wording required is really important. I would hope your father realises the potential for confusion – not least given your sister’s precarious accommodation arrangements – and sees the sense of providing clarity to ensure all his children get to benefit from his inheritance.If your father is not prepared to be so pedantic in his will and to trust the future of his home to you as a group, you can only hope there will be a meeting of minds and a willingness to compromise. That or be prepared for an acrimonious debate and the prospect of expensive court hearings.Please send your queries to Dominic Coyle, Q&A, The Irish Times, 24-28 Tara Street, Dublin 2, or by email to dominic.coyle@irishtimes.com with a contact phone number. This column is a reader service and is not intended to replace professional advice