Supply date confussion

[jamesbrown]

See here. Unless it fits a special case, if you're issuing a VAT invoice, a single tax point / invoice date is fine, but the client probably wants to know the period for which the invoice applies, assuming it's a T&M contract

[GeorgeGeorge]

As a typical IT contractor working through a Ltd company, issuing invoices per calender month, and on the flat rate VAT scheme...

I understand it is a legal requirement to include both the Invoice Date and the Supply Date on the invoice.
However I see some conflicting information about what the supply date should be.

• It might be the same as the invoice date
• It might be the date the services were supplied. (the last day of the month)
• It might be date on which I receive payment. (which I can't know in advance)

My main on confusion is that because of the flat rate scheme, I think I should use the date of payment as the supply date. But at the time of writing the invoice I have know idea when the payment will be made.

What do other people use as the supply date? Or do you just not include it on your invoice?