Your letter needs to be more detailed. You need to explain in full how you meet each requirement, what income amount you are relying on, what documents you are supplying etc., along with the full details of the accommodation, plus the details of all your trips to see each other, along with the date you got engaged and the date and location where you got married.
For example:
To The Entry Clearance Officer,
I am writing to sponsor my wife's application for a settlement visa to join me in the UK. I am a UK citizen and have lived in the UK (or whichever UK country) since birth (or explain where you've lived if you have not lived in the UK since birth).
I meet the financial requirements under Category E of the financial requirements, using my self-employment income. I am a director of [company name] which I set up on X date/has been trading since X date. I am using my self-employment from the following financial year (give dates) to meet the requirement. During (said financial year), my total pre-tax income after expenses was £X, which is shown on (my tax return). I pay myself an income of £X/dividends of £X and am providing my payslips/dividend vouchers and bank statements to show this (or however you pay yourself). Please find enclosed in the document package all the required documents for Category E.
Once the visa has been approved, my wife and I have permission to live with my mother at her property in (town, country), located at the following address [list address]. This is a 4-bedroom property, which will house myself, (wife's name) and my mother, and will therefore not be overcrowded.
My relationship with xxxxxx started in July 2017, when we met online. My first trip to the USA was in August 2017, and we have met in person 5 times since then for extended periods (give the dates of every visit). When we are apart, we keep in contact on a daily basis via WhatsApp & email. We got engaged on X date and we married in city, country on Y date. We are now choosing to settle together in the UK because (wife's name) likes the country and also because I have my business here and somewhere to live here.
Yours Faithfully,
Your Name
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