Most law firm merger value is gained or lost in the first 90 days post-completion. The deal itself takes 12-20 weeks from heads of terms to completion. The integration that follows determines whether the combined firm hits the merger thesis or quietly underperforms while the deal lawyers move on.
This guide is the structured playbook for the senior partner project-managing the integration. We cover the regulatory-side mechanics (SRA notification, PII continuity, client matter novation), the financial-side mechanics (accounts integration, payroll merger, client money transition), and the human-side dynamics that determine whether the inherited team stays.
The first 90 days: a structured timeline
Days 1-7 — completion week
- SRA notification filed within 7 days of any material change (new partners, new COFA/COLP, structural change)
- Client matter novation letters drafted and approved (legal team)
- Client account opened in new firm's name (if not already)
- PII continuity confirmed in writing by the broker for all acquired matters
- Payroll for inherited team set up in acquiring firm's system; first PAYE submission date confirmed
- Case management system access provisioned for inherited fee-earners
- VAT registration position confirmed (acquirer may need to register, deregister, or update VAT group)
Days 8-30 — operational integration
- Client matter novation letters issued (bulk for high-volume, bespoke for sensitive)
- Client money for transferred matters moved interbank to the new client account
- Reconciliation of pre- and post-merger client account positions
- Inherited fee-earners' SRA practising certificates updated for the new firm
- Inherited team's professional subscriptions transferred
- Conflict check run across combined client base; any conflicts surfaced and managed
- Office account merger or co-ordination depending on the deal structure
Days 31-60 — financial integration
- Accounting system migration: inherited firm's matters loaded into the acquirer's PMS or accounting system
- WIP reconciliation: opening WIP balances confirmed and matched to the deal completion accounts
- Time-recording onboarding for inherited fee-earners
- Bookkeeping team merger or service-provider transition
- Management accounts for the first post-merger month produced and reviewed
- First five-weekly client account reconciliation across combined ledgers
Days 61-90 — bedding in
- Cultural integration: combined team meetings, partnership / LLP agreement amendments to admit any inherited members
- Client communications: post-merger introduction letters to clients of the inherited matters
- Marketing and brand integration: website, letterhead, email signatures, professional directory listings
- First quarterly partner review meeting in merged form
- Project close-out and lessons-learned documentation
Client matter novation: the practical mechanics
What counts as a client matter
Every open file the firm holds for a client. Active matters with ongoing work; matters in billing; matters effectively closed but where the file hasn't been formally closed and client money hasn't been returned.
What clients need to consent to
The matter being handled by a different firm. Solicitors are appointed by clients; that appointment is personal to the firm (or to the named solicitor within the firm, depending on the engagement letter terms). A simple change of firm name (e.g., the firm is rebranding) doesn't always require consent. A substantive change of firm (different SRA-regulated entity) typically does.
Bulk novation letters
For high-volume, low-complexity matters (residential conveyancing, low-value debt recovery), bulk novation letters are typical. The letter explains the change, names the new firm, gives the client a contact for questions, and notes that continued instruction implies consent. Most clients accept without comment.
Bespoke novation
For sensitive or complex matters (personal injury, family, criminal, high-value commercial litigation), each client is contacted individually with a tailored explanation. Some clients will want to interview the new partner. A minority will choose to move their matter elsewhere — built into the deal economics as expected attrition.
Client money for transferred matters
The SRA Accounts Rules require client money for transferred matters to be held in the new firm's client account from completion. The mechanics:
- On completion day, the acquiring firm has a designated client account ready
- Interbank transfer of total client money from seller's client account to acquirer's client account
- Each matter ledger transferred individually; reconciliation evidence retained
- Any residual or unmatched balances investigated and resolved before the next reconciliation
SRA notification and consent
Material change notification (within 7 days)
Several events trigger a 7-day notification obligation to the SRA:
- Change in firm ownership or control
- New COLP or COFA appointed
- Change in practice structure (sole practitioner to partnership, partnership to LLP)
- Material change in regulated activities
When ABS licence application is required
The Alternative Business Structure (ABS) regime applies when:
- Non-solicitor ownership or control of an SRA-regulated entity
- Mixed ownership (solicitors and non-solicitors)
- Specific structures that take the firm outside the Recognised Body regime
ABS licence application is a substantive process — 3-6 months typically. If the deal structure requires ABS, the application should be in flight before deal completion to avoid a gap in regulatory status.
PII continuity: the critical detail
PII is non-negotiable. The acquired matters must be covered from the moment of completion. The structure depends on deal type and policy renewal timing.
Option 1 — Seller's policy runs to renewal
If the seller's PII renewal is months away, the policy can continue covering the acquired matters until renewal. At renewal, the acquiring firm picks up coverage on its own policy (extending limits if needed) and the seller's policy moves to run-off cover for the pre-completion period.
Option 2 — Acquirer's policy extended
The acquiring firm's PII broker arranges an immediate extension to cover the acquired matters from completion. This is the cleanest structure if the acquirer's renewal is close to completion and the new policy can be sized appropriately.
Option 3 — New combined policy from completion
For larger deals, a new combined policy is sometimes negotiated from completion, sized to cover the merged firm's combined practice. The seller's policy moves to immediate run-off.
Run-off cover
SRA requires run-off cover for at least 6 years after a firm ceases (or the cessation of a specific entity within a deal). Run-off premium typically equates to 1.5x to 3x the final annual premium, paid upfront. Buyer and seller need to be clear about who pays — typical structure is the seller pays from the deal proceeds.
Accounts integration: the practical work
Opening balances and WIP
The deal completion accounts set the opening position. Acquired WIP is loaded into the new firm's accounting system at the agreed valuation. The acquired matter ledgers are imported with their client money balances. Goodwill is recognised at the agreed value, post-April-2019 amortisation begins.
Time recording and billing
Inherited fee-earners need access to the acquirer's time-recording system from day 1. The first month typically shows lower-than-normal recorded time as the team learns the new system. Billing of inherited matters resumes once the case management migration is complete (typically by day 21-30).
Management accounts
The first post-merger management accounts (covering the first full month post-completion) require care. Pre- and post-completion figures need to be reconciled. The opening balance sheet needs to match the deal accounts. Management accounts producing a "merger" line that explains the impact help partners read the numbers without confusion.
VAT
The combined firm's VAT position needs review. Possible scenarios: existing VAT group extended to cover acquired firm, new VAT registration if the deal creates a new entity, deregistration of the acquired firm if its registration is no longer needed. Get the position confirmed with HMRC pre-completion to avoid VAT-period gaps.
People integration
Equity and fixed-share partners from the acquired firm
Typically admitted as members of the acquiring firm's LLP (or partners of the partnership) on agreed terms. The LLP agreement is amended to admit them. Their capital contribution from the old firm may or may not transfer depending on deal terms. FA 2014 Salaried Member Rules apply from the date of admission.
Salaried fee-earners
Transferred under TUPE in most acquisition scenarios. Employment terms preserved at the transfer point. PAYE on the acquiring firm from the next pay date. Contract amendments thereafter are between the acquiring firm and the employee.
Support staff
Same TUPE treatment as salaried fee-earners. Often the area where headcount rationalisation eventually happens (duplicate finance, marketing, HR functions in a merged firm) — but the rationalisation should not happen in the first 90 days. Stabilise first.
Common things that go wrong
PII gap at completion
The broker says "we'll sort it" and doesn't. Acquired matters are uninsured for a window. Worst-case scenario. Prevent by getting written PII continuity confirmation in advance of completion as a condition precedent.
Client money mismatch at first reconciliation
The transferred client money doesn't reconcile to the inherited matter ledgers. Often because of un-billed disbursements, mis-posted receipts in the seller's system, or matters not fully closed. Fix by treating the first reconciliation as a clean-up exercise and resolving all variances before the next monthly cycle.
Inherited team attrition
Senior fee-earners leave in the first 6 months because they don't fit the acquirer's culture or weren't bought in to the deal. The economics of the merger fall apart if the key fee-earners leave. Prevent by involving them in the integration design pre-completion, not communicating to them post-completion.
Cultural friction
The combined firm doesn't operate as one. Two factions persist. Eventually one wins, but the lost productivity in the meantime is significant. Prevent by senior partner explicit leadership on culture from day 1.
What we'd do if you brought us in
Our post-merger integration engagement covers the financial and operational mechanics. We project-manage:
- Client account migration and reconciliation
- Accounting and payroll system integration
- WIP and matter ledger import
- VAT position review and HMRC liaison
- First three months of management accounts in the merged form
- SRA Accountant's Report co-ordination for the first merged year-end
The regulatory solicitor handles the SRA notification mechanics, novation letters, and partnership/LLP agreement amendments. We work in tandem.
If you've signed heads of terms or are in due diligence on a deal, book a 30-minute scoping call below.