Has this sale and capital gain been declared twice?

Hello all. My partner sold her house last year and did all the sums to estimate the CGT (I am helping her to deal with it). She declared the gain online and got the same estimate of CGT from the HMRC website, which she paid immediately. In her SA declaration for 2022/23 (submitted August 2023) she completed the additional form SA108 with the same figures for the capital gain. When she received the HMRC Tax Calculation in September it said she still owed CGT (payable before Jan 31 2024). BUT the "new" estimate for the capital gain is exactly TWICE what she declared, and the amount of CGT that the Tax Calculation says she has already paid is exactly TWICE what she actually paid. She immediately wrote a letter to HMRC (Oct 2nd) with these details. There was no reply and in December she phoned the SA helpline who acknowledged receipt of the letter but said it would be dealt with in February. When we pointed out that the deadline for paying was the end of January, she passed it to the "Technical Dept" and said we would hear within 6 days. But so far, no reply. What we surmise has happened is that the figures (for everything) have been registered twice - once in the online CGT declaration and once in the SA108 form: but obviously there was only 1 sale of 1 house. We don't know what to do now. It seems in everyone's interest (HMRC and my partner) that this is settled before the end of January otherwise there is going to be a lot of extra work to get a refund of overpaid tax. But what action can we take? Can we withhold the SA calculation on the grounds that our letter is waiting to be dealt with? Would we still be fined and have interest to pay? Help please! and Thanks in advance.

Hi
The SA108 also asks you to complete the boxes to show if the gain has already been reported and any tax paid. based on your query, this has not been done hence the additional charge due.You can telephone 0300 200 3310 to have this corrected. this can be done by a technical advisor on the phone rather than wait for the letter to be actioned.

Hi, Thank you so much for your reply. In fact, since posting the first message (above) I think I have located the problem exactly. In the form SA108 we declared the capital gain twice: once in box 9 and once in box 52.1. Yes, I know - in hindsight that was dumb; but at the time it seemed the right thing to do (we live in France). We also filled in the tax already paid, in boxes 10 and 52.4, so the doubling of both figures is explained. We tried the number you suggested and it was answered after more than an hour waiting time - only for the battery on our portable fixed-line phone to give up a few minutes later, cutting us off from the advisor. I guess we'll try again tomorrow. Unfortunately the original SA was filed on paper, so we can't even log in to amend the tax return. Unless it is possible to file a new return online? ( It didn't use to be possible to file online from France, but maybe that's changed? ) Thanks again!

Success this morning, long wait but not as long as yesterday. Problem corrected by Tech Dept. Yippee. As an aside, over 50 odd years of dealing with HMRC staff I've always found them to be helpful, knowledgeable and efficient. This time was no exception. (Applause) . Getting through to actually find a person to speak with ... well, the less said the better.

Hi megadyne,
You will need to amend your tax return to remove the entry in 52.1 to 52.4, as these boxes are for non UK residents to complete, if they dispose of a UK property or land.  
You can do this online by logging into your personal tax account and amending your tax return or by submitting a paper SA108 marked as an amendement.  
Capital Gains summary (2023).  
The latter option will take longer to be processed.
Thank you.

To the person who posted this query ( Megadyne?). Thank you so much and to the HMRC admin response. We could not understand why my husband appears to owe so much tax this year but guessed it might be to do with CGT on a commercial property he sold in July 2023. Having read the above comment we went back to look at his self-assessment form ( we kept a copy) and sure enough, he had not filled in Boxes 21 ' gains and losses reported on Real Time Transaction Scheme ' or Box 22 Tax on gains already Paid". We had both reported and paid ( have the receipt). Hoping the phone no. given by HMRC here is still valid and that we can get this corrected as you did. Thanks again. We were so worried until we worked out the problem , thanks to you.