6 month / 18,600 in the 12 months prior query

Hi can somebody confirm I have is correct regarding the rules about the Spouse visa maintenance requirement of £18,600 - say $29,000.

I'm currently moving back to the UK (I'm British) in September, then my US spouse is joining me sometime after. When I arrive in the UK I will not have employment.

If I start work say November, once I have one months pay evidence my spouse can apply for he visa as long as I've made $29,000 in the previous 12 months. So from November 2015 going back to November 2014?

The longer it takes me to start work, the 12 month value starts counting down - until you get to the stage where you no longer have made the $29,000 the previous year and so then have to show 6 months of current pay at that rate?

I'm basically trying to figure out how long I have to start work before I lose my 12 months previous luxury?

I currently make around $45,000 so by my atrocious mathematical ability I have about 4 months to secure employment and qualify without the 6 month stint?

p.s. I realize a job offer is a much better option.

Looks right to me.

My maths (assuming your current employment is salaried, and not variable):

$45,000 annually = $3,750 per month
£18,600 approximates to $29,000

Yes, you have a window of about 4 months to find employment to use the 12 months previous income (category B).

Months Employed  Months Unemployed  Effective Income
           1                        11                         $3,750
           2                        10                         $7,500
           3                         9                         $11,250
           4                         8                         $15,000
           5                         7                         $18,750
           6                         6                         $22,500
           7                         5                         $26,250
           8                         4                         $30,000 *meets the requirement
           9                         3                         $33,750 *meets the requirement
          10                        2                         $37,500 *meets the requirement
          11                        1                         $41,250 *meets the requirement

Great, love your breakdown too thanks!

Do I need to provide a letter of authentication from my current employer regarding the pay stubs?

If I was to ask for this say end of August would I still be able to use this letter for a Visa submission say December? I think I read evidence has to be valid no more than 28 days prior?

If they are original payslips, you do not need a letter.  You need need to submit the bank statements that show the deposit of each one though.