Most late payments are not disputes - they are friction. An invoice that is slightly unclear or slightly incomplete gets set aside "to deal with properly later," and later has a way of becoming three weeks.
No due date, or a vague one like 'ASAP' - clients pay against a date, not a feeling
Missing or unclear payment details - if your bank details are hard to find, paying you becomes a two-step task instead of one
Vague line item descriptions like "Work carried out" - if the client has to guess what they are paying for, they will ask before they pay
An invoice number that looks inconsistent with previous ones - it can read as disorganised, which invites more scrutiny, not less
Sending the invoice to the wrong contact - always confirm who actually handles payment, especially for larger clients with a separate accounts team
No VAT breakdown when you are VAT registered - some finance departments will not process an invoice at all until this is correct
Waiting to send the invoice - the single biggest one. A perfect invoice sent two weeks late still gets paid two weeks late
None of these are dramatic mistakes - they are small pieces of friction that stack up. A tool that generates a complete, correctly formatted invoice by default (rather than relying on you to remember every detail each time) removes most of this list automatically.