Sole Trader - Accounting for pre-PAYE'd Income

I’m working one day a week lecturing at a university, and am providing the service under my company brand. As a lecturer, they count me as faculty staff, and therefore get paid through the salary system. However, despite my insistence on zero rating tax, they are taking PAYE contributions (and adding holiday pay) anyway.
I could ignore this as a pre-taxed income, but I want it to show on my accounts, and the salary is being paid into my business bank account, so tagging is needed anyway.
How should I account for this to ensure that pre-tax income is accounted for whilst the payments made don’t match?
(My thoughts were to pay down a monthly invoice partly from the current bank account, and partly from the proprietors drawings account - but something makes me think this isn’t quite the right solution).

If the income is taxed at source then it’s not self-employment turnover and should not be attributed to an invoice. It’s effectively your own personal money that is being paid in to the business bank account, so I’d tag it as a transfer from drawings.