Booking System Development: What to Specify Before You Get a Quote

Every booking system looks the same from the customer's side: pick a thing, pick a time, pay. Almost all of the cost sits behind that screen, in the rules about what can be booked when, by whom, and what happens when plans change.

Buy first, unless

Calendly, Acuity, Bookwhen, SimplyBook and their peers are good and cheap. Use one if your booking is a person and a time slot with simple rules. Build when the rules are yours: multiple resources per booking, pricing that depends on combinations, availability that depends on staff qualifications, or a booking that is one step in a longer process you also want to control. Our build versus buy guide applies here exactly.

The decisions that shape the system

What is being booked

A time slot with a person (consultations, lessons). A resource for a period (rooms, vehicles, equipment). A place on a fixed event (courses, classes, tours). A combination (a room plus a trainer plus equipment). Each is a different data model, and combinations are where the cost concentrates.

Availability rules

Opening hours are easy. Staff rotas, buffer times between bookings, minimum notice, maximum advance booking, seasonal changes, bank holidays, blackout dates, per-resource exceptions: each is a rule, and rules interact. Write yours down as sentences before you talk to anyone. "A treatment room can be booked in 30-minute slots between 9 and 6, with 15 minutes between bookings, by any therapist qualified for that treatment" is a specification. "Normal availability" is not.

Pricing and payment

Fixed price, price by duration, price by option, member pricing, promotional codes, deposits with the balance later, packages of sessions, gift vouchers. Stripe or a similar provider handles the card processing; the logic around it is yours to specify. Deposits and balances roughly double the payment work compared with pay-in-full.

Changes and cancellations

Can customers reschedule themselves? Up to when? What is refunded, and is it automatic? What happens to a deposit? Who is notified? This is the area most often left to "we'll handle it manually", which means the staff side of the system never gets built and the emails never stop.

Staff and admin

The customer screens are a fifth of the system. Staff need to see the day, move bookings, block time, take phone bookings, override prices, issue refunds and see who has not paid. Reporting for the owner: utilisation, revenue by service, no-show rates. Budget for this side explicitly.

Notifications

Confirmation, reminder (email and SMS - SMS reminders measurably cut no-shows), change notices, review requests after. Each is a template plus a rule about when it fires.

Integrations worth having

• Calendar sync (Google, Outlook) for staff, two-way.
• Accounting (Xero, QuickBooks) so payments become invoices without re-keying.
• Your CRM, if the booking is the start of a relationship rather than the whole of it - see our CRM development page for how those connect.
• Your website, so booking is embedded rather than a link to somewhere else.

What it costs

A single-resource booking system with fixed prices, pay-in-full, self-service rescheduling and a staff calendar: £7,000 to £15,000, 5 to 8 weeks. Multiple resources, rules-based availability, deposits and balances, packages, SMS reminders, calendar and accounting sync: £15,000 to £35,000, 8 to 14 weeks. Marketplaces (many providers, each with their own availability and payouts) are a different product with a different budget. We build these as custom web applications and quote fixed after scoping.

A specification you can send today

Two examples from different industries

A physiotherapy clinic

Six practitioners, two rooms, treatments of different lengths, some requiring specific equipment, some practitioners qualified for some treatments only. Patients book online, pay a deposit, receive an SMS reminder, can reschedule up to 24 hours before. The clinic needs a day view per room and per practitioner, waiting lists for cancellations, and package tracking for block bookings. Availability is the hard part: a treatment is bookable only where a qualified practitioner, a suitable room and any required equipment are all free. That is a mid-band system: rules-based availability, deposits, packages, SMS.

A training company

Scheduled courses at fixed dates with capacity limits, delivered by trainers at venues, with early-bird pricing, group discounts, corporate invoicing rather than card payment for some clients, and certificates issued on completion. The "availability" is capacity, which is simpler; the complexity is in pricing rules, invoicing paths and the post-booking workflow. Different shape, similar band.

Things people forget to specify

• Time zones, if any customers or staff are outside the UK.
• What happens at the exact moment two people try to book the last slot.
• Who gets notified when a customer cancels, and whether the slot reopens automatically.
• Refund policy in code: partial, full, credit note, none - and by when.
• Accessibility of the booking screens, which is a legal consideration for many UK businesses and a good idea for all.
• Reporting: which numbers the owner looks at weekly.

Launch without losing bookings

Run the new system alongside the old one for a week with a small group, keep the phone booking route open throughout, migrate future bookings rather than history, and launch on the quietest day of your week. Every booking system launch we have seen go wrong went wrong on a Monday morning with no fallback.

Why availability rules dominate the cost

Every rule is a condition the system must check before offering a slot, and rules interact. "Room B is unavailable on Tuesdays" is one rule. "Room B is unavailable on Tuesdays except for practitioner C, who can use it for treatment D only if the equipment is not booked elsewhere" is four rules with dependencies, and the system has to evaluate all of them in the time it takes a page to load. Write your rules as plain sentences and count them; a system with five is a different project from one with twenty-five, and an agency can only price what it can count.

The same applies to pricing. "£60 an hour" is one rule; "£60 an hour, £50 for members, £45 for the second hour, 10 percent off with a code, deposit of 20 percent refundable up to 48 hours" is six. None are hard individually; together they are most of the work.

If you already run a bought booking tool, export a month of bookings, cancellations and refunds before scoping. Real data shows the agency the shape of your demand, how often plans change, and which rules actually fire - and it usually removes a third of the features from the wish list.

Six headings: what is booked; availability rules as sentences; pricing and payment; change and cancellation policy; what staff need to do; what it must connect to. Two paragraphs under each is enough for a fixed quote and will save a week of discovery. Send it over when it is ready, or before, if you would rather talk it through.