Shouldn't the subbies send you an invoice cos technically they're a supplier so a wage slip wouldn't be appropriate. But I get that most of them think they are employed & are 'staff' so think it is a wage slip & just want it as easy as possible for themselves, never mind you. 

If they are VAT registered you could consider self-billing but it would be a manual thing, on excel & then saved as pdf. 

But if they're not VAT registered, I don't think you're allowed to do self-billing.

Shouldn't the subbies send you an invoice cos technically they're a supplier so a wage slip wouldn't be appropriate. But I get that most of them think they are employed & are 'staff' so think it is a wage slip & just want it as easy as possible for themselves, never mind you. 

If they are VAT registered you could consider self-billing but it would be a manual thing, on excel & then saved as pdf. 

But if they're not VAT registered, I don't think you're allowed to do self-billing.