is nor even just if the Estate is 'small'. Dad died 2021 and had a will, everything to his wife - mum. We did not need to contact / deal with the Probate Office and there is no record there.
They sold their house 6 months before he died and moved to a ground floor appartment during that process there was an overlap of 1 month when they owned both properties so funds had to be moved around and loaned briefly. The house and then appartment were owned in joint names. Upon receipt of the house sale money repayments were made and the surplus placed in 2 JOINT bank accounts. Most of the old accounts had been closed and things like the car ownership and insurance moved to mum during the change of address process, Dad being terminally ill.
An associate of the solicitor who dealt with the house sale and held their Wills visited (offices were closed - COVID) & confirmed that no Probate application was necessary unless the banks, Equiniti for shares or the companies holding his old life policys required it to release funds and they did not, a death cert, copy of the Will and the Small Estate form was sufficient to them all. Each had different thresholds eg £10k but googling I see is now 50k for some banks. The Inland Revenue were also happy on the tax side.
Had he had his share of the savings in his own sole name then Probate would have been needed as was above the Small Estate limits of the banks, they had just downsized house to appartment.
The estate of married couples passes to the surviving spouse. It will be a different matter when mum dies Probate will be needed then for sale of the appartment and dealing with the accounts and distribution.
Eg if I google 'northern ireland probate' the National Bereavement Service quick guide says
"You may not need a grant if the deceased left less than £20,000, or if everything was jointly owned with someone else in which case everything passes automatically to the surviving joint owner." OR being the applicable bit.