A Perennial Problem for most businesses, especially contractors

Is it 
 - End of the month +60 days (Up to 90 Days)
 - End of the month +30 days (Up to 60 Days)
 - Invoice date +30 days (30 Days)
 - End of the month
 - A few days after invoice
 - Stage payments on a project

The Construction Index recerntly reported that the government is to legislate on this and maximise the period to 60 days , beyond which penalties will apply

https://email.theconstructionindex.co.uk/t/r-l-tuliuukd-hjiydikdyk-jy/