Flowed Down, Not Assumed: Five Back-to-Back Gaps to Test Before Signing a Subcontract
The phrase appears in almost every subcontract preamble we see: the subcontractor accepts the obligations of the main contractor under the main contract insofar as they relate to the subcontract works. It reads as a single, tidy transfer of risk. In practice it is a claim, not a fact. The main contract may not have been provided, the relevant clauses may not survive translation into a smaller scope, and the two documents may simply contradict one another. Where they do, the subcontract almost always prevails for the parties who signed it — which means the back-to-back label offers cold comfort when a dispute arrives.
The sensible response is not to reject back-to-back arrangements. They are a legitimate and often efficient way to align risk across a supply chain. The response is to test the claim before signature, clause by clause, and to record what was actually agreed. What follows are five gaps that recur most often in UK commercial subcontracts, and a method for tabulating them that a commercial team can run without external counsel.
Why the label so often overstates the position
Back-to-back transfer works cleanly only where four conditions hold: the main contract terms are disclosed, the obligations are capable of applying to the subcontract scope, the timing mechanisms are compatible, and neither document has been amended in a way that breaks the link. In our experience at least one of those conditions fails on most projects. Sometimes the main contract is described but not supplied. Sometimes it is supplied in a form marked as superseded. Sometimes the flow-down is expressed as a general incorporation of terms that a subcontractor could not reasonably price.
None of this is necessarily improper. It is, however, a reason to treat the phrase as a prompt for enquiry rather than a conclusion.
Gap one: payment mechanics
The Housing Grants, Construction and Regeneration Act 1996, as amended, sets a statutory floor for payment terms, but it does not align two contracts automatically. A main contract may allow thirty days from a payment application to a payment notice, with a further period before the final date for payment. A subcontract that compresses the same sequence into fourteen days places the subcontractor's cash flow on a different clock. If the main contractor's own payment is contingent on certification upstream, the subcontract needs to say so explicitly, and the subcontractor needs to understand that the contingency is a payment risk, not a scheduling detail.
Pay less notices are the practical flashpoint. A subcontractor that assumes the upstream notice regime applies will miss the window created by its own document.
Gap two: notice periods and time bars
Time bars are where back-to-back claims fail most expensively. A main contract may permit a compensation event notice within eight weeks; a subcontract may reduce that to seven days, or require notice to be given to the main contractor before it is given to the client. Both are common, and both are enforceable.
Where the subcontract imposes a shorter window than the main contract, the subcontractor carries a compliance burden it may not have priced. Where it imposes a longer one, the main contractor may find itself unable to pass the notice upstream in time. Neither party benefits from an unclear position, but the party who discovers it after the event bears the greater cost.
Gap three: liability caps and indemnities
Liability is rarely symmetrical and rarely flows down intact. A main contract may be uncapped for a defined category of loss, or capped at a multiple of the contract sum. A subcontract may offer a lower cap, exclude consequential loss, or include an indemnity that operates independently of the cap. Two questions matter: is the subcontract cap expressed as a standalone figure or by reference to the main contract, and does the carve-out list match?
A cap defined by reference to an upstream document is only useful if that document is fixed, disclosed and unlikely to be renegotiated. Where the main contract is still being settled, a referenced cap is not a cap at all.
Gap four: programme and sectional obligations
Programme duties are frequently assumed rather than scrutinised. A main contract may carry sectional completion dates carrying liquidated damages at one rate; the subcontract may carry a single completion date with damages calculated differently, or with no damages mechanism at all and a general obligation to proceed regularly and diligently. Possession and access provisions may be drafted around a site the subcontractor will never control.
The practical test is to write the dates down side by side and check that the subcontract's dates, durations and damages are arithmetically capable of supporting the upstream obligations. Where they are not, the gap should be resolved before award, not at the first delay event.
Gap five: security, retention and termination
Security packages rarely mirror one another. A performance bond at main contract level may have no counterpart in the subcontract; retention percentages and release triggers may differ; a parent company guarantee may be required of the subcontractor but not offered by anyone upstream. Termination rights can diverge just as sharply, particularly where the main contractor's right to terminate for convenience has no equivalent flowing down.
For a subcontractor, the question is whether the security it is asked to provide is proportionate to the security it can rely on. For a main contractor, it is whether the arrangement leaves a gap that will be exposed if the employer terminates the main contract.
A comparison table that does the work
A single A3 sheet, completed jointly, resolves more ambiguity than a long exchange of correspondence. Set out the main contract position in one column, the proposed subcontract position in the next, and record the agreed resolution in a third. Where the documents diverge, state whether the divergence is intended, priced and accepted by both parties.
| Check | Main contract | Proposed subcontract | Resolution recorded |
|---|---|---|---|
| Payment notice and final date for payment | 30 days / 14 days | 14 days / 7 days | Compressed timing accepted; cash flow modelled |
| Notice window for delay events | 8 weeks | 7 days | Agreed; notice template issued at award |
| Liability cap | Contract sum, uncapped for specified losses | 50% of subcontract sum | Referenced cap removed; standalone figure agreed |
| Sectional completion and damages | Two sections, £X per week | Single date, no damages | Sections adopted in subcontract |
| Retention and bond | 3% retention, no bond | 5% retention, 10% bond | Bond reduced to 5%; retention aligned |
Two disciplines make the table useful. First, every entry should cite a clause reference in both documents, so that the exercise is verifiable rather than impressionistic. Second, the resolution column should record the commercial consequence, not merely the legal position — a shortened notice window is only a problem if the team cannot meet it.
Recording the outcome
The final step is the least glamorous and the most valuable: attach the completed table to the executed subcontract as a signed schedule, or at minimum record it in the contract award note. A short covering statement confirming that the disclosed main contract is the executed version, that no further amendments are anticipated, and that the divergences listed are intended, will do more to prevent later argument than any amount of preamble language.
Back-to-back is a reasonable ambition. It becomes a reliable arrangement only when someone has actually checked where the flow stops. That check takes an afternoon at tender stage and considerably less than a dispute at the other end.
