Captital tax won a shed

Hi, could anyone explain captial tax allowance to me I am thinking of buying a new shed as old one not big enough to store all business stuff. But it will also have my garden tools in. How much can I put through books?

Also do my pension contributions come out of my earnings so bring down how much tax, NI I need to pay?

Thanks in advance for any help xx

Sorry that should read on a shed not won a shed! ( wish I had) :laughing:

As small sole traders we use Cash Basis for our tax so there's no capital allowance to worry about.
Cash basis - GOV.UK
Just estimate the % of the shed which is for childminding and put it through as an expense, that's my understanding.
If you are not sure you really should just check it with an accountant to make sure.

Regarding pension contributions...

It doesn't come out of your earnings as such, but when you fill in your online self assessment there is a section to put in your pension payments.