Guides
Invoicing and billing guides
How to write the invoice, charge the right VAT, bill your time and get paid on schedule. Worked examples and wording you can use today.
Invoicing basics
- 8 min readHow to invoice clients (step by step)What an invoice must say, when to send it and who to send it to, with a complete worked example and the EU and UK rules behind each field.
- 6 min readHow to invoice a client as a freelancerYour name, your VAT position and your day rate on one page. What a freelance invoice needs, a worked example, and what to ask a new client before the first bill.
- 6 min readHow to invoice professional servicesHourly, fixed fee or retainer: what each line should say, how much detail clients need, and a worked example that keeps fees, expenses and disbursements apart.
- 4 min readHow to convert a quote to an invoiceThe customer said yes. What carries over from the quote, what has to change, and how to bill it in one go or in stages without retyping a line.
- 6 min readQuote vs invoice vs receiptOne offers a price, one asks for money, one confirms you got it. What each does legally and for VAT, where pro formas fit, and every document on one job, worked through.
- 6 min readHow to number invoicesWhat EU and UK rules actually require, which format to use, what to do with gaps and cancelled invoices, and a two-minute check that your sequence holds together.
- 4 min readHow to issue a credit noteOnce an invoice has gone out, you correct it with a new document. What a credit note must say, when you need one, and how the numbers work.
- 7 min readInvoice email templates clients can act onSeven invoice emails to copy, from a first invoice to a corrected one, with subject lines an accounts team can find later and the facts they need in the first two lines.
- 8 min readOverdue invoice reminder email sequenceAn optional nudge before the due date, then five steps to a final notice, with wording to copy for each, plus what to send when a customer has paid part or disputes it.
- 9 min readHow to charge a late fee on an invoiceWhat EU and UK law lets you charge a late-paying business, this half-year's rates, a worked calculation with the rounding trap, and wording to copy for your terms and the invoice.
Getting paid
- 7 min readInvoice payment terms examplesNet 14, Net 30, end of month, early-payment discounts and stage payments: what each term means, wording to copy, the legal limits in the EU and UK, and how to choose.
- 6 min readHow to invoice a deposit and final paymentTwo invoices, two numbers, one total. How to word each one, what VAT does on the deposit under Article 65, and a worked example that adds up to the quote.
- 6 min readHow to invoice and record partial paymentsA part payment needs no new invoice. How to record it, what to tell the customer, what happens to the VAT, and when instalments do call for separate invoices.
- 6 min readHow to invoice a monthly retainerThe same invoice, on the same day, naming the period. Advance or arrears, what happens to VAT, how to handle hours over or under the allowance, and wording for the agreement.
- 5 min readAged receivables report: how to read it and act on itA worked aged receivables report, what each column tells you, what to do about each age bucket, and how to build one in a spreadsheet if your software doesn't have it.
- 5 min readInvoice reconciliation for service firmsMatch every invoice to the bank, prove the total, and check that all your work got billed. A month-end method with a worked example and what to do when the numbers disagree.
- 5 min readHow to invoice reimbursable expensesIts own line, a description and the right VAT. A worked invoice with a fee, a recharge and a disbursement, the VAT-on-VAT mistake, and wording to agree before you spend.
- 6 min readHow to write a rate increase letter to clientsLetters to copy for hourly, retainer and project clients, how much notice to give, what a client can do about it, and how much work you can lose before a rise costs you money.
- 6 min readStatement of account: a worked example for client billingWhat a statement of account is, a complete worked example, open-item or balance-forward, the cover note to send with it, and what to do when a client's figures disagree.
International invoicing and VAT
- 7 min readHow to invoice international clientsWhere the sale is taxed, what the invoice has to say, and how the answer changes for EU, UK and other overseas clients. With a decision table and a worked example.
- 6 min readHow to invoice EU clients (VAT, reverse charge & VIES)When you charge no VAT to an EU client, what the invoice must show, how goods differ from services, where the €10,000 threshold applies and what you report afterwards.
- 6 min readVAT invoice template fields, explainedEvery field a VAT invoice needs under Article 226, what goes wrong with each, the extra mentions some invoices need, and a filled-in example with two VAT rates.
- 6 min readReverse-charge invoice wording: example and checklistThe exact words an EU reverse-charge invoice needs, wording to copy for goods, services and UK construction, a sample invoice, and a checklist to run before you send it.
- 6 min readHow to check a VAT number in VIESThe steps, what each VIES result means, why a real number can show as invalid, how to keep proof of the check, and what to do about UK numbers.
- 6 min readCommercial invoice versus tax invoiceOne gets goods through customs, the other records the sale for tax. What each must contain, when you need both, and a worked export with the same figures on each.
- 6 min readHow to invoice in a foreign currencyWhat the EU and UK require when you bill in another currency, which exchange rate to use for VAT, and a worked example from invoice to payment with the exchange loss.
- 7 min readVAT on reimbursable expenses and disbursementsMost expenses you pass on to a client carry VAT. The test for a true disbursement, a worked invoice with the sums, and the mistake that charges VAT on VAT.
Time tracking and invoicing
- 5 min readHow to track billable hoursWhat to record for each block of client work, when to record it, and a worked time log you can copy into a spreadsheet today.
- 5 min readHow to turn billable hours into an invoiceFrom a month of time entries to an invoice a client will pay: the cut-off, the review, how much detail to show, and a worked example that reconciles to the hour.
- 5 min readHow to track billable vs non-billable hoursWhich tasks you can charge for, a short set of reason codes for the rest, and how to read a month's numbers to see where the unpaid hours actually go.
- 7 min readHow projects work in ERPFlow: boards, cards, deadlines and peopleWhat a project is in ERPFlow, how to split work into boards, what a card holds, how deadlines and notifications behave, and what projects don't do.
- 4 min readLogging time in ERPFlow as a team memberHow to record your time on a project card, why you add to the figure already there, how to keep a note of who did what, and where the hours show up.
- 5 min readA practical billable-time workflow for accountantsWhat to record time against, a monthly close you can follow, how to stop out-of-scope work leaking, and how to see what each fixed fee earns per hour.
- 6 min readBilling for travel time to sites and client meetingsThe ways to charge for travel, what each one costs the client on a long trip and a short one, how to split a shared trip, and wording for your quote.
- 6 min readA consulting time tracking workflow that supports billingEngagement codes, time entries a client won't query, a draft bill before every invoice and a monthly reconciliation. A workflow for consultants, with one month worked through to the invoice.
- 5 min readA freelance time tracking and invoicing workflowOne log, one Friday check and one billing day. The whole routine for a freelancer who bills by the hour, with a time log layout, wording for the client and a month's hours worked into an invoice.
- 5 min readHow to track billable hours for an agencyAgency hours run across several people, several rates and retainers that overrun quietly. How to set up the codes, what counts as billable, and how to check a retainer before the month is gone.
- 5 min readResource planning for service teams: see who is free and who is overbookedA weekly grid that compares each person's available hours with what's already promised, and what to do with the result. A spreadsheet method with a worked week, for small service teams.
- 5 min readTeam timesheet template: a weekly layout your invoices can useA weekly timesheet layout you can copy into a spreadsheet, filled in for two people, with the formula that turns it into invoice quantities and the sums checked at each step.
- 6 min readHow to track time and materials for client billingA job sheet layout for labour and materials, a markup clause to copy, how VAT applies, and what to test in a time and materials app, with one heating job worked through to the invoice.
- 5 min readHow to track billable hours by projectGive each project a code, make every time entry name one, and keep worked, billed, written-down and unbilled hours in one running table. The setup, the checks and what a project total can hide.
Rates and profitability
- 4 min readBlended hourly rate: how to calculate it and when to quote oneThe formula, a worked example, why a simple average overcharges, what a change in staffing does to your margin, and wording for the quote.
- 5 min readHow to calculate a charge-out rate for your staffThe formula, how many hours a person can really bill in a year, a worked example by grade, and the margin mistake that quietly costs thousands a year.
- 6 min readBilling increment chart: 6, 10 and 15-minute tablesConversion tables from minutes worked to billable decimal hours for 6, 10 and 15-minute billing, with what each increment does to a real day's bill.
- 5 min readBudget hours vs actual hours: tracking a fixed-fee design projectTurn a fixed fee into an hours budget, compare it weekly with real progress, forecast the finish, and know what to do when the hours run ahead.
- 5 min readUtilisation versus billable hours in professional servicesBillable hours are a count and utilisation is a ratio. How each is calculated, why the same hours can mean different things, and how to work out a utilisation target from your own costs.
- 6 min readProject profitability: bill by person and see what each project earnsA spreadsheet method: each person's hours at their billing rate and at their cost rate, then the difference. With a worked project, a fixed-fee comparison and the mistake that flatters most margins.
- 6 min readWrite-down vs write-off: what each one means for your billingA write-down reduces what you charge. A write-off gives up on what you're owed. When each applies, which document it needs, and where VAT bad-debt relief comes in, with one job worked through.
Billing by industry
- 8 min readProgress billing: how to invoice a project in instalments as the work movesHow to split a contract into invoices tied to agreed stages or measured work, keep a running total, and handle variations and VAT, with a worked example of one contract billed across four invoices.
- 6 min readConsultant hourly vs retainer billingWhen a consultant should bill by the hour and when a monthly retainer pays better, with a decision table, six months billed both ways, and retainer wording you can copy.
- 6 min readA law firm time and billing workflowThe eight steps from engagement letter to paid bill: recording time with a usable narrative, reviewing a pre-bill, and where client money rules come in, with a worked example.
- 6 min readHow to write an invoice for accounting servicesWhat an accountant's invoice has to show: the right entity, the period, fixed fees and extras on separate lines, and disbursements outside the VAT sum, with a worked example and wording to copy.
- 7 min readAIA G702 and G703: how the application for payment adds upG703 holds the line-by-line progress and G702 turns its totals into the amount due. Every column and line explained, with a worked application to check your own figures against.
- 6 min readAdditional services in architecture: how to agree, record and invoice themExtra work gets paid when it was agreed first. What counts as an additional service, wording to get it agreed in writing, a register to keep it straight, and how it reads on the invoice.
- 5 min readHow much of an architect's week is billable?About 70% for staff and under half for owners, on RIBA's figures. Why benchmarks disagree, how to work out your own target by role, and what it does to the hourly rate you need.
- 7 min readHow to write an architect's fee proposal from your own past hoursPrice the job from what similar jobs actually took. How to pull past hours per stage, scale and adjust them, turn them into a stage-by-stage fee, and word the assumptions that protect it.
- 6 min readArchitecture project management: track team time against stage fees and bill clientsTurn each stage fee into a budget of hours, compare hours used with work done every week, and bill on the agreed trigger. A worked tracker that spots an overrun while you can still act.
- 7 min readThe fees section of an accountant's engagement letterWhat the fees section of an engagement letter has to answer, clause wording you can adapt, and why a fee spread over twelve months needs an exit clause, with the arithmetic.
- 6 min readHow to write an engineering fee proposalDefine the deliverables, estimate hours by grade, choose a fee basis and write down what you've assumed. A worked build-up, a table of fee bases and assumption wording to copy.
- 5 min readFixed fee accounting: how to price it and check it paysHow to build a fixed fee for an accounting client from hours and a target rate, then test it client by client, with worked figures showing how a healthy average can hide a loss.
- 7 min readHow staffing and recruitment agencies invoice clientsWhat temp staffing, contingent recruitment and retained search each bill for, when, and how the sums work, including bill rate against margin, placement rebates, VAT on wages and transfer fees.
- 5 min readLump sum vs hourly fees for design and engineering workWho carries the risk under each fee basis, a decision table for design and engineering jobs, the point where a lump sum stops paying, and fee wording to copy for both.
- 6 min readHow to set up a project numbering systemWhich project number format to choose, how to handle phases and variations, why project and invoice numbers should stay separate, and the spreadsheet traps that break a numbering scheme.
- 6 min readRetainage on an invoice: the deduction, the running total and the releaseHow to show retainage on each progress invoice, keep the running total, bill the release, and handle UK retention and VAT. Worked figures and wording included, plus where the law varies.
- 7 min readRIBA stage fees: how to split a fixed fee across the Plan of WorkRIBA publishes the stages but no fee split. How to divide a fixed fee from your own estimated hours, adjust it for risk and cash flow, and word the payment triggers in the appointment.
- 6 min readWIP report: what your firm has earned but not yet billedA WIP report compares the value of work done on each job with what you've invoiced. How to value hourly and fixed-fee work, read the result, build one in a spreadsheet and act on it.
Team planning and timesheets
- 6 min readInvite your team to ERPFlowWhere to send the invitation, which role to choose, how many people each plan includes, and what a new member can see and change on day one.
- 6 min readTime off tracker: a layout that also tells you your capacityA leave log tells you who is away. Add one weekly grid and it also tells you how many hours the team has left. The layout, the balance sum and a worked example.
- 5 min readWhy every person on the team should log timeOne person's missing hours can make a losing job look profitable. What complete time records let you decide, what they cost to keep, and when they aren't worth it.
- 6 min readTimesheet policy: a practical example for project firmsA one-page timesheet policy to copy: who logs, in what unit, by when, how corrections work, and why a project timesheet isn't automatically a working time record.
- 5 min readCapacity planning template: available hours against bookings, week by weekA capacity planning template you can build in a spreadsheet: each person's available hours, what's booked, what's left, and how to read four weeks ahead before saying yes to a job.
- 6 min readExpense claim policy for a small project firmA one-page expense claim policy to copy: what staff can claim, what needs approval first, what evidence to keep, and how a claim reaches the client's invoice.
- 6 min readMileage claim template for project firmsA mileage claim template to copy, with HMRC's 2026 to 2027 rates (55p, not the old 45p), a worked example across the 10,000-mile band, and which site journeys count.
- 5 min readTime by task: where each person's hours went, month by monthHow to build a time by task report from timesheet lines, what it looks like for a small team, how to read four months of it, and which task codes are worth having.
- 6 min readTimesheet approval process for project firmsA weekly timesheet approval process for a small project firm: who approves, a timetable that fits your invoicing, what to check, and wording for sending a timesheet back.
FAQ
ERPFlow guides: common questions
Everything you need to know about ERPFlow. Can't find the answer? We're here to help.
Contact usWho are the ERPFlow guides written for?
The ERPFlow guides are written for owners and office managers of small service businesses who send their own invoices. They assume no accounting background, and each guide works through a real example with numbers.
Do I need ERPFlow to use these guides?
No. Every guide works on its own, with whatever invoicing tool or spreadsheet you use today. Where ERPFlow handles a step, the guide says how, and where ERPFlow doesn't do something, the guide says that too.
Are the ERPFlow guides tax or legal advice?
No. The guides explain how invoicing, VAT and billing generally work, but the rules depend on your country and your situation. Check anything with a tax or legal consequence with your accountant before relying on it.
Does ERPFlow have time tracking?
Not yet. Time tracking in ERPFlow, including converting tracked time into invoices, is coming soon. Today a card in ERPFlow Projects records time spent, typed in as hours and minutes, and those totals add up per project and per customer. Hourly work is billed by entering a rate and a quantity on the invoice.
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