To manage an account that has a mix of taxable and non-taxable transactions, add an unlinked account in Calxa to split the budget. This is useful for income accounts where you might have a mix of taxable and tax-free products or services.
Navigate to: Settings > Chart of Accounts > Add new account
If the tax code on your main account is taxable (eg GST or VAT), set the new one as tax-free or exempt
Split your budget between the original line (taxable) and the new line (tax free)
The cashflow forecast will then only calculate GST/VAT on the main account budget
You could use an Account Tree header set as summary only to combine the two account lines for your reporting.