A plumber, sparky or labourer working across more than one of your jobs in a week is a normal way to keep a good subbie busy and a schedule moving. The problem shows up at invoicing: their bill usually arrives as one number for the period, not helpfully broken down by which job got which hours — and dumping the whole thing onto whichever job feels biggest at the time distorts every job it touches.

Why a single lump invoice breaks job costing

If a subbie's whole week gets tagged to one job, that job's cost looks worse than it should, and the other jobs they worked on look artificially cheap. Both numbers are wrong in a way that compounds: the overcharged job looks like a bad one to quote again, and the undercharged jobs look more profitable than they actually were — exactly the kind of quiet distortion that leads to underpricing similar work later.

Get the split at the source, not after the fact

The cleanest fix is agreeing the split before the invoice arrives, not reconstructing it afterwards. A subbie who logs which job they were on each day — even a rough daily note — makes splitting the eventual invoice a five-minute job instead of a guess. Where that's not practical, asking for the invoice itself to be broken down by job, or by day, shifts the admin to the point where the information is freshest.

What a fair split actually needs

  • Days or hours per job — the most defensible basis for a split, and the easiest for a subbie to actually provide.
  • Materials they supplied, split separately — if the subbie is also supplying materials, don't assume those split the same way as their labour time did.
  • A note on anything unusual — a job that took a subbie longer than expected is worth knowing about on its own, not just folded into a total.

A worked example

Say an electrician invoices for a week split across three of your jobs: two full days on one job, one and a half on a second, and a day and a half on a third. Tag the whole invoice to whichever job happens to be open when it's logged and two jobs are wrong by a meaningful margin. Split by the days actually worked on each — even from a rough note rather than a formal timesheet — and all three jobs carry an honest share of a cost that was always going to be real regardless of how it's recorded.

When it's genuinely not worth splitting

A subbie doing a half-day top-up on a second job while mostly working one main site isn't always worth the admin of a precise split — a reasonable estimate, or simply tagging the smaller amount to the secondary job, is good enough when the amounts involved are small relative to the job's overall cost. The effort should scale with how much the split actually matters to either job's total.

How Site Wallet handles this

A single subcontractor invoice can be logged once and allocated across every job it actually covers, with each job carrying only its own share of the cost — so a busy subbie working three sites in a week doesn't distort any of them. The full invoice stays attached for the record, while each job's running total reflects only what it genuinely owes.

FAQ

Should I ask subbies to invoice per job instead of per week?

It's worth asking for, especially for a subbie you use regularly — a per-job invoice or a daily breakdown saves both sides the reconstruction work later, even if it means slightly more admin on their end.

What if a subbie can't or won't provide a breakdown?

A reasonable estimate based on what you know of their time on each site is better than tagging the whole invoice to one job — imperfect information split fairly beats accurate-looking information attached to the wrong place entirely.

Does this matter for tax purposes as well as job costing?

Yes — accurate per-job costs feed directly into knowing which jobs were genuinely profitable, which matters for both future pricing decisions and for having a clear, defensible record if your own expense claims are ever reviewed.