Jirlam

I own a part share in a number of parcels of agricultural land,(the land is owned by 3 people 2 @ 25% and the other at 50%) the land was gifted the current owners by my father in 2010 and at that time he carried out a valuation so Im clear about the value at that time. The land has been sold recently over a 2 year period for tax efficiency and clearly I need to report the capital gains. The completion dates are spread over the 2 years concerned. The agreement with the agents and solicitors was to invoice all costs disbursements etc when all lots were finally sold. There were specific problems removing some of the tenants which went some way to protracting the sales. I rang HMRC on 11th Jan 23 to establish how this would be dealt with (I was completing my 21/22 self assessment). I hadn't at that time received the full sale proceeds. The operative suggested that my CGT declaration be held back to 22/23 when all costs were known and invoiced and all the sale proceeds had been processed. Ive tried to complete my 22/23 SA but clearly this only refers to a single tax year and thus I can only claim a single allowance. I have some but not all records of improvements to the land which I believe can be offset against the gain now attributable. My brother was the other 50% owner but unfortunately he took his own life some years ago and those records are very sketchy. My father died in 2017 so again records are sketchy. I have put together a spreadsheet which shows valuation in 2010, the sale value and to the best of my knowledge all the capital improvements along with all transfer costs for 201 and all our current cost. I have a subsequent gain for each of the parcels broken down into separate tax years. Im unsure of how to submit this now?? Can you provide some guidance please.