1, How much can I contribute in my private pension to reduce/reclaim 40% liability?
£5,590 occupational pension contributions
I am presuming your employees contributions made are deducted from gross pay - ie your taxable pay has been reduced - calcs will be different if your employees pension contributions are deducted from net salary - Note employers contributions are non relevant.
Based on 63,205 being your taxable pay for the year and £6,000 personal payment into pension with tax relief added in of £1,500 - gross pension contribution
I am presuming you don't live in scotland and for simplicity i have presumed you will not be eligible for marriage allowance transfer
Ok Higher rate threshold is £45,000
And child benefit lower threshold is £50k
Your higher rate threshold is extended by £7,500 (pension contributions made directly by you)
so thats 45000+7500 = 52500
Your taxable income is 63,205
Difference £10,705 - 80% of this is 8564 - so you would need to put 8564 cash into pension (with basic rate relief added in ) to remove yourself from higher rate tax.
Similar calcs for child benefit
63205-50000-7500= £5,705 - so you are £5,705 gross above child benefit limit - 80% of 5705 = 4564 you would need to put in cash to make child benefit tax charge go away.
2, I am the only paid worker in our marriage with 3 children hence the need to stay below the 50k taxable pay. If I pay more and get below the 40% tax bracket can I claim part of my wife's tax allowance I think it's around 1100 pounds? Ie about 250 net.
extreme warning this allowance is all or nothing - if you are £1 into higher rate tax you loose all of the allowance transfer - so £1 of savings interest could foul things up.
I will do second post with calcs adjusted for marriage allowance transfer