Paragraph 30 Calculation of deduction of tax and contributions of self-employed earnersI1

on the basis of the amount of chargeable income; and

as if that income were assessable to income tax at the basic rate F1, or in the case of a Scottish taxpayer, the Scottish basic rate, of tax applicable to the assessment period less only the F2personal reliefs to which the applicant is entitled under Chapters 2, 3 and 3A of Part 3 of the Income Tax Act 2007 as are appropriate to his circumstances.

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the amount of Class 4 contributions (if any) which would be payable under section 15 of the SSCBA (Class 4 contributions recoverable under the Income Tax Acts) at the percentage rate applicable to the assessment period on so much of the chargeable income as exceeds the lower limit but does not exceed the upper limit of profits and gains applicable for the tax year applicable to the assessment period; but if the assessment period is less than a year, those limits must be reduced pro rata.

except where paragraph (b) applies, the earnings derived from the employment less any expenses deducted under sub-paragraph (3)(a) or, as the case may be, (3) of paragraph 29;

in the case of employment as a child minder, one-third of the earnings of that employment.