At the end of each month, update your bookkeeping software with your invoices, cash received and expenses.
It will then show your corporation tax (and VAT if applicable) liabilities to date, and crucially the amount you can pay yourself.
There will also usually be personal tax to pay on the amount you pay yourself, and possibly a student loan repayment if you have one. To give you an idea of how much to set aside for this bill each January, your bookkeeping software includes a table of expected personal tax and loan liabilities based on various income brackets.
- Keep your earnings under £3,750/month to stay within the basic rate tax threshold (for the personal tax year ending 5/4/18) and avoid paying higher rate personal tax if possible.